Diagnosis and treatment of cancer using anti-gpr49 antibody

ABSTRACT

Antibodies that bind to a GPR49 protein and have cell proliferation inhibitory activity against cells expressing the GPR49 protein are disclosed. Cell proliferation inhibitory activities are cytotoxic activities such as antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity. Pharmaceutical compositions, cell-proliferation inhibitors, and anticancer agents containing an antibody of the present invention as an active ingredient are also disclosed. Examples of cancer include gastric cancer, colon cancer, hepatocellular carcinoma, lung cancer, prostate cancer, ovarian cancer, Ewing&#39;s sarcoma, and glioma. Furthermore, methods for diagnosing cancer by detecting expression of a GPR49 protein or a gene encoding a GPR49 protein, and diagnostic agents and kits to be used in these methods are also disclosed.

TECHNICAL FIELD

The present invention relates to methods for diagnosing and treatingcancer, and anticancer agents.

BACKGROUND ART

GPR49 molecule is a protein encoded by the ENSG00000139292 gene of humanchromosome 12q12, and its amino acid sequence characteristics haverevealed that it is a member of the LGR family (Leucine-rich GPCRfamily, hereinafter referred to as the LGR family), which is a hormonereceptor family of G-protein coupled seven-transmembrane proteins(Non-patent Document 1). Members of the LGR family include hormonereceptors such as LHR, TSHR, and FSH, as well as LGR7 and LGR8, ligandsof which are relaxin, insulin-like peptide 3 (INSL3), and such(Non-patent Document 2). All ligands are known to comprise heterogeneouspeptides, and mainly transmit signals via cAMP. The LGR family has astructure comprising a seven-transmembrane protein region and anN-terminal long extracellular region. In the extracellular region, thereare 9 to 17 repeats of a leucine-rich region (leucine-rich repeat: LRR)comprising of 25 amino acids or so. GPR49 comprises 17 LRRs (Non-patentDocument 1). According to analysis of TSHR and such, G-protein-coupledsignal transduction occurs when a ligand binds to this extracellular LRRwith high affinity, and also to the second extracellular loop region(Non-patent Document 3; Pharmacology & Therapeutics 103, 21 (2004)). Theligands of GPR49 have not yet been identified, but since ligands ofDLGR2, a closely-related LGR of Drosophila, were found to be Bursiconcomprising Burs and Pburs (partner of Bur) which are molecules of theBMP antagonist family, there are reports that the ligands of LGR4, LGR5(GPR49), and LGR6 with yet unknown ligands may also be BMP antagonists(Non-patent Document 4 and Non-patent Document 2). As for the functionsof these molecules, analyses of knockout mice have suggested that theyare involved with ankyloglossia (ankylogenesis) (Non-patent Document 5).Furthermore, from gene expression analyses of hair follicle stem cells,they are speculated to be involved in the proliferation of stem cells(Non-patent Document 6).

With regard to involvement in cancer, Yamamoto et al. have reported thatGPR49 is highly expressed in liver cell cancer patients (Non-patentDocument 7), and also that expression of GPR49 at the mRNA level isupregulated particularly in patients with mutations in beta-catenin.Furthermore, Ito et al. have mentioned GPR49 as an example of a moleculehighly expressed in gastric cancer patients based on Affymetrix Genechipdata analyses (Patent Document 1).

It has been reported that expression of GPR49 is upregulated in coloncancer and ovarian cancer, and upregulation of expression at the mRNAlevel is observed at 64% (25/39) of colon cancer patients and 53%(18/33) of ovarian cancer patients (Non-patent Document 8).Immunostaining using PoAb has revealed that it is expressed in thenormal tissues of placenta and skeletal muscles (Non-patent Document 8).As for its involvement with canceration, focus formation assay showedthat NIH3T3 subjected to only gene transfer did not show focus formationin four weeks, but cells supplemented with a culture supernatantobtained from a SW620 culture (conditioned medium) showed focusformation within three weeks. Accordingly, GPR49 is assumed to induceligand-dependent canceration. Accumulation of subG1 cells and apoptosisinduction was observed in siRNA experiments. It is suggested that GPR49may have functions of inhibiting apoptosis induction in colon cancercells.

However, based on expression of cancer cell lines it has also beenreported that although GPR49 expression is upregulated in colon cancer,ovarian cancer, glioma, and melanoma, such an upregulation is not seenin breast cancer and lung cancer (Non-patent Document 8).

-   [Patent Document 1] WO 2000/071710-   [Non-patent Document 1] Mol. Endocrinology 12, 1830 (1998)-   [Non-patent Document 2] Journal of Endocrinology 187, 333 (2005)-   [Non-patent Document 3] Pharmacology & Therapeutics 103, 21 (2004)-   [Non-patent Document 4] PNAS 102, 2820 (2005)-   [Non-patent Document 5] Molecular and Cellular Biology, 24, 9736    (2004)-   [Non-patent Document 6] Nature Biotechnology 22, 411 (2004)-   [Non-patent Document 7] Hepatology 37, 528 (2003)-   [Non-patent Document 8] Cancer Biology & Therapy 5, 419 (2006)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An objective of the present invention is to provide novel methods fordiagnosing and treating cancer, or to provide novel cell proliferationinhibitory agents and anticancer agents.

Means for Solving the Problems

The present inventors discovered that not only the GPR49 gene but alsothe GPR49 protein are highly expressed in cancer cells such as gastriccancer, colon cancer, hepatocellular carcinoma, lung cancer, ovariancancer, Ewing's sarcoma, and glioma. Furthermore, the present inventorsproduced monoclonal antibodies against the GPR49 protein and discoveredfor the first time that the GPR49 protein having a molecular weight of100 kDa is cleaved and divided into 60-kDa and 40-kDa fragments. Sincethe N-terminal 60-kDa fragment is cleaved and is secreted to the outsideof the cell, it is useful as a diagnostic marker for cancer.Furthermore, the C-terminal 40-kDa fragment may be useful as a target oftherapeutic antibodies.

Furthermore, the present inventors determined the complement-dependentcytotoxicity (CDC) and also the antibody-dependent cell-mediatedcytotoxicity (ADCC) of anti-GPR49 antibodies, and discovered that theanti-GPR49 antibodies have CDC activity and ADCC activity againstGPR49-expressing cells. Using toxin-bound antibodies, the presentinventors also discovered an activity that leads to cell damage ofGPR49-expressing cells. From the above-mentioned findings, the presentinventors discovered that the anti-GPR49 antibodies are effective fordiagnosing, preventing, and treating various types of primary ormetastatic cancers, and completed the present invention. Morespecifically, the present inventors discovered that GPR49 is useful as atool for treating or diagnosing cancers in which GPR49 expression isupregulated such as gastric cancer, colon cancer, hepatocellularcarcinoma, lung cancer, ovarian cancer, Ewing's sarcoma, and glioma, andcompleted the present invention.

That is, the present invention provides antibodies that bind to a GPR49protein. Furthermore, the present invention provides antibodies thatbind to a GPR49 protein, and have a cytotoxic activity against cellsexpressing the GPR49 protein. Preferably, the cytotoxic activity is ADCCactivity or CDC activity. The present invention also provides antibodiesto which a cytotoxic substance is conjugated.

Furthermore, the present invention provides pharmaceutical compositionscomprising an antibody that binds to a GPR49 protein as an activeingredient. The present invention also provides cell proliferationinhibitory agents comprising an antibody that binds to a GPR49 proteinas an active ingredient. The present invention also provides anticanceragents comprising an antibody that binds to a GPR49 protein as an activeingredient.

Alternatively, the present invention provides pharmaceuticalcompositions comprising an antibody that binds to a GPR49 protein andpharmaceutically acceptable carriers. More specifically, the presentinvention provides:

[1] an antibody that binds to a GPR49 protein, and which has cellproliferation inhibitory activity against cells expressing the GPR49protein;[2] the antibody of [1], wherein the cell proliferation inhibitoryactivity is cytotoxic activity;[3] The antibody of [2], wherein the cytotoxic activity isantibody-dependent cytotoxic activity;[4] the antibody of [2], wherein the cytotoxic activity iscomplement-dependent cytotoxic activity;[5] the antibody of any one of [1] to [4], wherein a cytotoxic substanceis bound to the antibody;[6] the antibody of [5], which has an internalizing activity;[7] the antibody of any one of [1] to [6], which suppresses cancer cellproliferation;[8] the antibody of [7], wherein the cancer cell is any one of gastriccancer cells, colon cancer cells, liver cancer cells, lung cancer cells,ovarian cancer cells, Ewing's sarcoma cells, and glioma cells;[9] the antibody described in any of (1) to (20) below:(1) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 5 as CDR1, the amino acid sequence of SEQ ID NO: 6 as CDR2,and the amino acid sequence of SEQ ID NO: 7 as CDR3;(2) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 10 as CDR1, the amino acid sequence of SEQ ID NO: 11 as CDR2,and the amino acid sequence of SEQ ID NO: 12 as CDR3;(3) an antibody comprising the H chain of (1) and the L chain of (2);(4) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 15 as CDR1, the amino acid sequence of SEQ ID NO: 16 as CDR2,and the amino acid sequence of SEQ ID NO: 17 as CDR3;(5) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 20 as CDR1, the amino acid sequence of SEQ ID NO: 21 as CDR2,and the amino acid sequence of SEQ ID NO: 22 as CDR3;(6) an antibody comprising the H chain of (4) and the L chain of (5);(7) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 25 as CDR1, the amino acid sequence of SEQ ID NO: 26 as CDR2,and the amino acid sequence of SEQ ID NO: 27 as CDR3;(8) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 31 as CDR2,and the amino acid sequence of SEQ ID NO: 32 as CDR3;(9) an antibody comprising the H chain of (7) and the L chain of (8);(10) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 35 as CDR1, the amino acid sequence of SEQ ID NO: 36 as CDR2,and the amino acid sequence of SEQ ID NO: 37 as CDR3;(11) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 40 as CDR1, the amino acid sequence of SEQ ID NO: 41 as CDR2,and the amino acid sequence of SEQ ID NO: 42 as CDR3;(12) an antibody comprising the H chain of (10) and the L chain of (11);(13) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 45 as CDR1, the amino acid sequence of SEQ ID NO: 46 as CDR2,and the amino acid sequence of SEQ ID NO: 47 as CDR3;(14) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 50 as CDR1, the amino acid sequence of SEQ ID NO: 51 as CDR2,and the amino acid sequence of SEQ ID NO: 52 as CDR3;(15) an antibody comprising the H chain of (13) and the L chain of (14);(16) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 66 as CDR1, the amino acid sequence of SEQ ID NO: 67 as CDR2,and the amino acid sequence of SEQ ID NO: 68 as CDR3;(17) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 71 as CDR1, the amino acid sequence of SEQ ID NO: 72 as CDR2,and the amino acid sequence of SEQ ID NO: 73 as CDR3;(18) an antibody comprising the H chain of (16) and the L chain of (17);(19) an antibody having one or more amino acid substitutions, deletions,additions, and/or insertions in the antibody of any of (1) to (18),which has equivalent activity as the antibody of any of (1) to (18);(20) an antibody that binds to the same epitope as the GPR49 proteinepitope bound by the antibody of any of (1) to (18);[10] the antibody of any one of [1] to [9], comprising a human constantregion;[11] the antibody of [10], which is a chimeric antibody, humanizedantibody, or human antibody;[12] a pharmaceutical composition comprising the antibody of any one of[1] to [11] as an active ingredient;[13] a cell proliferation-suppressing agent comprising the antibody ofany one of [1] to [11] as an active ingredient;[14] an anticancer agent comprising the antibody of any one of [1] to[11] as an active ingredient;[15] the anticancer agent of [14], wherein the cancer is any cancerselected from the group consisting of gastric cancer, colon cancer,hepatocellular carcinoma, lung cancer, ovarian cancer, Ewing's sarcoma,and glioma;[16] a method for diagnosing cancer, comprising detecting a GPR49protein or a gene encoding a GPR49 protein;[17] the diagnostic method of [16], comprising detecting a GPR49protein;[18] the diagnostic method of [17], wherein the GPR49 protein detectionis performed using an antibody that binds to a GPR49 protein;[19] a method for diagnosing cancer, comprising the steps of:(a) providing a sample collected from a subject; and(b) detecting a GPR49 protein contained in the sample of (a) using anantibody that binds to the GPR49 protein;[20] a method for diagnosing cancer, comprising the steps of:(a) administering to a subject a radioisotope-labeled antibodycomprising an activity to bind to a GPR49 protein; and(b) detecting accumulation of the radioisotope; and[21] the diagnostic method of any one of [16] to [20], wherein thecancer is any cancer selected from the group consisting of gastriccancer, colon cancer, hepatocellular carcinoma, lung cancer, ovariancancer, Ewing's sarcoma, and glioma.The present invention also provides:[22] a method for suppressing cell proliferation using the antibody ofany one of [1] to [11];[23] a method for treating or preventing cancer, which comprises thestep of administering the antibody of any one of [1] to [11]; and[24] use of the antibody of any one of [1] to [11] in the manufacture ofa cell proliferation-suppressing agent or an anticancer agent.

Effects of the Invention

Since the anti-GPR49 antibodies of the present invention havecomplement-dependent cytotoxicity as well as antibody-dependentcell-mediated cytotoxicity against GPR49-expressing cells, and when atoxin is conjugated to them, they have activities of leading to celldamage in GPR49-expressing cells, these antibodies are effective fordiagnosing, preventing, and treating various types of primary ormetastatic cancers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the expression profile of human GPR49 in normal tissues.The values were obtained from Exon Array analysis, and higher the value,higher the mRNA expression level.

FIG. 2 shows the expression profile of human GPR49 in gastric cancercell lines and in tumor sites of removed gastric cancer tissues. Thevalues were obtained from Exon Array analysis, and higher the value,higher the mRNA expression level.

FIG. 3 shows the expression profile of human GPR49 in tumor sites ofremoved Ewing's sarcoma, small cell lung cancer, and lung adenocarcinomatissues. The values were obtained from Exon Array analysis, and higherthe value, higher the mRNA expression level.

FIG. 4 shows the expression profile of human GPR49 in ovarian cancercell lines and in tumor sites of removed ovarian cancer tissues. Thevalues were obtained from Exon Array analysis, and higher the value,higher the mRNA expression level.

FIG. 5 shows a series of photographs depicting the detection of inducedexpression of GPR49 by monoclonal antibody 2U2E-2. They show that theantibodies specifically recognize GPR49 induced by adding 1 μL and 10 μLof doxycycline (Dox), and that the antibodies recognize the same bandsas those obtained when the HA-tag attached to the N-terminus is detectedusing anti-HA-tag antibodies.

FIG. 6 depicts a series of photographs showing the detection of GPR49protein in the cell lysate from DG44 cells forcedly expressing GPR49 andcolon cancer cell line LoVo transfected with GPR49 siRNA, usingmonoclonal antibodies 2U1E-1 and 2U2E-2. In cells transfected with siRNA507, 508, and 509, the expression of GPR49 was suppressed. (−) indicatescells not transfected with siRNA, and “con” indicates cells transfectedwith control siRNA. In addition to the 100-kDa band, the 40-kDa bandindicated by an arrow disappeared with 2U1E-1 and the 60-kDa bandindicated by an arrow disappeared with 2U2E-2; therefore, these bandsare GPR49-derived bands.

FIG. 7 shows a series of photographs depicting the detection of GPR49 bymonoclonal antibodies through immunoprecipitation of the cell lysate ofHA-GPR49-expressing DG44 cell line 2B10. 100-kDa and 40-kDa bands weredetected with 2U1E-1 and 100-kDa and 60-kDa GPR49 bands were detectedwith 2U2E-2. HRP-labeled anti-mouse IgG(H+L) antibody (manufactured byJackson ImmunoResearch Laboratories) was used as a secondary antibody.

FIG. 8 is a photograph showing the detection of GPR49 by monoclonalantibodies through immunoprecipitation of the cell lysate of 2B10 (DG44cell expressing HA-GPR49). The 60-kDa GPR49 band was detected by allantibodies of the 2L series. To distinguish the band derived from the Hchain of the antibodies used for immunoprecipitation and the 60-kDaGPR49 band, HRP-labeled anti-mouse kappa antibody (manufactured bySouthern Biotech) was used as a secondary antibody.

FIG. 9 is a photograph showing detection performed on cell lysates ofvarious cancer cell lines by WB using monoclonal antibodies. The lanesin the photograph have their sample names indicated and are colon cancercell line LoVo, gastric cancer cell line NUGC-4, hepatocellularcarcinoma cell line Alexander, hepatocellular carcinoma cell line HepG2,hepatocellular carcinoma cell line Huh6, ovarian cancer cell lineKURAMOCHI, ovarian cancer cell line OVSAHO, glioma U251, Chinese hamsterovary cell DG44, and HA-GPR49-expressing DG44 cell line 2B10,respectively.

FIG. 10 is a graph showing CDC activity of GPR49 antibodies.

FIG. 11 depicts graphs showing ADCC activity of GPR49 antibodies againstDG44 cells expressing HA-GPR49.

FIG. 12 is a graph showing the cytocidal (cell-killing) activity due toantibody internalization using Mab-Zap. Each of the three bar graphsshows the results of measuring by WST8 assay the proportion of viablecells in a sample prepared by adding antibodies and Mab-Zap toGPR49-inducible 293 cell line B4 without GPR49 induction (left), asample prepared by adding antibodies and Mab-Zap to GPR49-induciblecells with GPR49 expression induction (middle), and a sample prepared byadding antibodies alone to GPR49-inducible cells with GPR49 expressioninduction (right).

FIG. 13 depicts the structure of GPR49 and the regions included in thedeletion mutants and GST-fusion proteins.

FIG. 14 depicts a series of photographs showing the reactivity of 2U1E-1and 2T15E-2 with GST-fusion proteins by WB.

FIG. 15 depicts a photograph showing the reactivity of monoclonalantibodies 2U1E-1 and 2U2E-2 against mouse GPR49 by WB. Both antibodiesreact with human (H) and mouse (M) GPR49.

FIG. 16 shows the results of evaluating binding activity by flowcytometry (FACS). The peaks indicated with a solid line show thereactivity to cancer cell lines, and the shaded regions show the peaksobtained when the cells are treated without antibodies. The horizontalaxis indicates signal intensity determined by the binding degree ofFITC-conjugated antibodies, and the vertical axis indicates the numberof cells.

BEST MODE FOR CARRYING OUT THE INVENTION GPR49

GPR49 is a seven-transmembrane protein which is a member of the LGRfamily. An amino acid sequence of human GPR49 and a gene sequenceencoding it are disclosed in NCBI Accession Nos. NP_(—)003658.1 (SEQ IDNO: 1) and NM_(—)003667.2 (SEQ ID NO: 2), respectively. In the presentinvention, a “GPR49 protein” refers to both the full-length protein andfragments thereof. “Fragments” refers to polypeptides comprising anyregion of the GPR49 protein, and they may not have the function of thenaturally-occurring GPR49 protein. Examples of the fragments includefragments comprising the extracellular regions of the GPR49 protein.Positions 1 to 556, 615 to 637, 704 to 722, and 792 to 800 in the aminoacid sequence of SEQ ID NO: 1 correspond to the extracellular regions ofthe GPR49 protein. Positions 557 to 579, 592 to 614, 638 to 660, 681 to703, 723 to 745, 769 to 791, and 801 to 823 in the amino acid sequenceof SEQ ID NO: 1 correspond to the transmembrane regions.

Preparation of Anti-GPR49 Antibodies

The anti-GPR49 antibodies used in the present invention may be of anyorigin, and may be of any type and in any form, as long as they bind toa GPR49 protein. Specifically, known antibodies such as non-human animalantibodies (for example, mouse antibodies, rat antibodies, and camelantibodies), human antibodies, chimeric antibodies, and humanizedantibodies can be used. In the present invention, the antibodies may bemonoclonal or polyclonal antibodies, but monoclonal antibodies arepreferred. Binding of antibodies to the GPR49 protein is preferably aspecific binding.

Anti-GPR49 antibodies to be used in the present invention can beobtained as polyclonal or monoclonal antibodies using well-knowntechniques. In particular, monoclonal antibodies derived from a mammalare preferable as the anti-GPR49 antibodies for use in the presentinvention. The monoclonal antibodies derived from a mammal includeantibodies produced by hybridoma, and antibodies produced by a hosttransformed by genetic engineering techniques with an expression vectorcontaining an antibody gene.

A monoclonal antibody-producing hybridoma can be prepared, essentiallyby using the following known technique. First, Animals are immunizedusing the GPR49 protein as a sensitizing antigen according to a generalimmunization method. Immunocytes that are obtained from the immunizedanimals are then fused to known parental cells by a general cell fusionmethod to obtain hybridomas. Furthermore, hybridomas that produce ananti-GPR49 antibody can be selected from these hybridomas by screeningfor cells that produce the antibodies of interest using a generalscreening method.

Specifically, monoclonal antibodies are prepared, for example, asfollows. First, the GPR49 protein for use as the sensitizing antigen foracquiring the antibodies can be obtained by expressing a GPR49 gene. Thenucleotide sequence of a GPR49 gene is disclosed in NCBI Accession No.NM_(—)003667.2 (SEQ ID NO: 2) and such. Specifically, after a suitablehost cell is transformed with a known expression vector in which thegene sequence encoding GPR49 is inserted, the desired human GPR49protein can be purified by a known method from the host cell or itsculture supernatant. Alternatively, a purified naturally-derived GPR49protein may be similarly used. Furthermore, as used in the presentinvention, a fusion protein prepared by fusing a desired partialpolypeptide of a GPR49 protein with another polypeptide may be used asan immunogen. For example, Fc fragments of antibodies, peptide tags, orsuch can be used to produce a fusion protein for use as an immunogen. Avector that expresses the fusion protein can be prepared by fusing thedesired genes encoding two or more kinds of polypeptide fragments inframe, and inserting the fused genes into an expression vector. Methodsfor producing fusion proteins are described in Molecular Cloning 2nd ed.(Sambrook, J. et al., Molecular Cloning 2nd ed., 9.47-9.58, Cold SpringHarbor Lab. press, 1989).

The GPR49 protein purified as described above can be used as asensitizing antigen for immunization of mammals. A partial peptide ofGPR49 can also be used as a sensitizing antigen. For example, thefollowing peptides can be used as a sensitizing antigen:

peptides obtained by chemical synthesis based on the amino acid sequenceof human GPR49;peptides obtained by incorporating a portion of the GPR49 gene into anexpression vector and expressing it; andpeptides obtained by degrading the GPR49 protein with proteases.

The region and size of GPR49 used as partial peptides are not limited.Preferred regions can be selected from the amino acid sequencesconstituting the extracellular domains of GPR49 (positions 1 to 556, 615to 637, 704 to 722, and 792 to 800 in the amino acid sequence of SEQ IDNO: 1). The number of amino acids constituting a peptide to be used asthe sensitizing antigen is at least three or more, for example five ormore, or preferably six or more. More specifically, peptides having 8 to50 residues, or preferably 10 to 30 residues can be used as sensitizingantigens.

Mammals immunized by these sensitizing antigens are not particularlylimited. To obtain monoclonal antibodies by the cell fusion method, theanimal to be immunized is preferably selected considering itscompatibility with the parental cells used for cell fusion. Generally, arodent is preferred as the animals for immunization. Specifically, mice,rats, hamsters, or rabbits can be used as animals for immunization.Alternatively, monkeys or such may be used as animals for immunization.

The above-described animals can be immunized with a sensitizing antigenaccording to a known method. For example, as a general method, mammalscan be immunized by injecting a sensitizing antigen intraperitoneally orsubcutaneously. Specifically, the sensitizing antigen is administered tomammals several times every 4 to 21 days. The sensitizing antigen isdiluted at an appropriate dilution ratio with Phosphate-Buffered Saline(PBS), physiological saline, or such, and then used for immunization.Furthermore, the sensitizing antigen may be administered together withan adjuvant. For example, the sensitizing antigen can be prepared bymixing with a Freund's complete adjuvant for emulsification.Furthermore, an appropriate carrier can be used for immunizing with thesensitizing antigen. Particularly when a partial peptide with a smallmolecular weight is used as a sensitizing antigen, the sensitizingantigen peptide is desirably conjugated to a carrier protein such asalbumin or keyhole limpet hemocyanin, and then used for immunization.

Meanwhile, monoclonal antibodies can be obtained by DNA immunization.DNA immunization is a method for immunostimulating by administering toan animal to be immunized a vector DNA constructed so that a geneencoding an antigenic protein can be expressed in the immunized animal,and allowing the immunogen to express in vivo. Compared to conventionalimmunization methods in which a protein antigen is administered, thefollowing advantages can be expected from DNA immunization.

Immunostimulation can be provided while maintaining the structure of amembrane protein such as GPR49.

There is no need to purify an immunogen.

On the other hand, it is difficult to combine DNA immunization withmeans for immunostimulation such as adjuvants. Since GPR49 has thestructural feature of being a seven transmembrane conformation, it wasexpected that induction of an immune response while maintaining thenaturally-occurring structure in vivo would be difficult. From suchstructural characteristics, actually obtaining by DNA immunizationmonoclonal antibodies that bind to GPR49, which is a protein belongingto the LGR family for which antibodies had been difficult to obtain, wasan unexpected achievement.

To obtain monoclonal antibodies of the present invention by DNAimmunization, first, a DNA that expresses a GPR49 protein isadministered to an animal to be immunized. A DNA encoding GPR49 can besynthesized by known methods such as PCR. The obtained DNA is insertedinto a suitable expression vector, and then administered to an animal tobe immunized. Commercially available expression vectors such as pcDNA3.1may be used as an expression vector. Conventional methods can be used toadminister a vector to an organism. For example, gold particles adsorbedwith an expression vector are shot into cells using a gene gun for DNAimmunization.

According to the findings of the present inventors, hybridomas thatproduce GPR49-binding antibodies could not be obtained efficiently frommice immunized by intraperitoneal administration of cells forcedlyexpressing GPR49. On the other hand, hybridomas that produceGPR49-binding antibodies could be obtained efficiently from miceimmunized using DNA immunization. In particular, the hybridomas ofinterest could be readily obtained from mice to which cells forcedlyexpressing GPR49 were administered after DNA immunization. That is, in apreferred method for obtaining the monoclonal antibodies of the presentinvention, a booster using GPR49-expressing cells is performed after DNAimmunization.

Mammals are immunized as described above. After confirming the desiredincrease in the amount of antibody in the serum, immunocytes arecollected from the mammals, and then subjected to cell fusion. Inparticular, splenocytes can be used as the preferred immunocytes.

A mammalian myeloma cell is used as a cell to be fused with theabove-mentioned immunocyte. The myeloma cells preferably comprise asuitable selection marker for screening. A selection marker conferscharacteristics to cells for their survival (or death) under a specificculture condition. Hypoxanthine-guanine phosphoribosyltransferasedeficiency (hereinafter abbreviated as HGPRT deficiency) and thymidinekinase deficiency (hereinafter abbreviated as TK deficiency) are knownas selection markers. Cells with HGPRT or TK deficiency havehypoxanthine-aminopterin-thymidine sensitivity (hereinafter abbreviatedas HAT sensitivity). HAT-sensitive cells cannot synthesize DNA in a HATselection medium, and are thus killed. However, when the cells are fusedwith normal cells, they can continue DNA synthesis using the salvagepathway of the normal cells, and therefore they can grow even in the HATselection medium.

HGPRT-deficient and TK-deficient cells can be selected in a mediumcontaining 6-thioguanine, 8-azaguanine (hereinafter abbreviated as 8AG),or 5′-bromodeoxyuridine, respectively. Normal cells are killed sincethey incorporate these pyrimidine analogs into their DNA. Meanwhile,cells that are deficient in these enzymes can survive in the selectionmedium, since they cannot incorporate these pyrimidine analogs. Inaddition, a selection marker referred to as G418 resistance providesresistance to 2-deoxystreptamine antibiotics (gentamycin analogs) fromthe neomycin-resistant gene. Various types of myeloma cells that aresuitable for cell fusion are known. For example, myeloma cells includingthe following cells can be used to produce the monoclonal antibodies ofthe present invention:

P3 (P3×63Ag8.653) (J. Immunol. (1979) 123, 1548-1550);

P3×63Ag8U.1 (Current Topics in Microbiology and immunology (1978) 81,1-7);NS-1 (Kohler. G. and Milstein, C. Eur. J. Immunol. (1976) 6, 511-519);MPC-11 (Margulies. D. H. et al., Cell (1976) 8, 405-415);

SP2/0 (Shulman, M. et al., Nature (1978) 276, 269-270);

FO (de St. Groth, S. F. et al., J. Immunol. Methods (1980) 35, 1-21);S194 (Trowbridge, I. S. J. Exp. Med. (1978) 148, 313-323);

R210 (Galfre, G. et al., Nature (1979) 277, 131-133), etc.

Cell fusions between the immunocytes and the myeloma cells areessentially carried out using known methods, for example, a method byKohler and Milstein et al. (Kohler, G. and Milstein, C., MethodsEnzymol. (1981) 73: 3-46).

More specifically, cell fusions can be carried out, for example, in aconventional culture medium in the presence of a cell fusion-promotingagent. The fusion-promoting agents include, for example, polyethyleneglycol (PEG) and Sendai virus (HVJ). If required, an auxiliary substancesuch as dimethyl sulfoxide may also be added to improve fusionefficiency.

The ratio of immunocytes to myeloma cells may be determined at one's owndiscretion, preferably, for example, one myeloma cell for every one toten immunocytes. Culture media to be used for cell fusions include, forexample, media that are suitable for the growth of myeloma cell lines,such as RPMI1640 medium and MEM medium, and other conventional culturemedium used for this type of cell culture. In addition, serumsupplements such as fetal calf serum (FCS) may also be added to theculture medium.

Cell fusion is carried out as follows. Predetermined amounts ofimmunocytes and myeloma cells are mixed well in the culture medium. PEGsolution pre-heated to around 37° C. is mixed to produce fused cells(hybridomas). In the cell fusion method, for example, mean molecularweight of about 1,000 to 6,000 PEG is usually added at a concentrationof 30% to 60% (w/v). Then, an appropriate culture medium described aboveis successively added to the mixture, and the sample is centrifuged toremove supernatant. This treatment is repeated several times to removethe unwanted cell fusion-promoting agent and others that are unfavorableto hybridoma growth.

Hybridomas thus obtained can be selected using a selection mediumappropriate for the selection markers carried by myelomas used for cellfusion. For example, cells with HGPRT and TK deficiencies can beselected by culturing them in a HAT medium (a medium containinghypoxanthine, aminopterin, and thymidine). More specifically, whenHAT-sensitive myeloma cells are used for cell fusion, cells thatsuccessfully fuse with normal cells can selectively grow in the HATmedium. Culture using the above-mentioned HAT medium is maintained for asufficient time to kill cells other than the hybridoma of interest(non-fused cells). More specifically, the hybridoma of interest can beselected, usually by culturing for several days to several weeks.Hybridomas that produce the desired antibody can then be screened andsingly-cloned by conducting a standard limiting dilution method.Alternatively, a GPR49-recognizing antibody can be prepared using themethod described in International Patent Publication No. WO 03/104453.

A desired antibody can be suitably screened and singly-cloned by ascreening method based on a known antigen-antibody reaction. Forexample, the antigen is conjugated to a carrier such as polystyrenebeads or the like, or a commercially available 96-well microtiter plate,followed by reaction with the culture supernatant of the hybridomas.Then, after the carrier is washed, it is reacted with an enzyme-labeledsecondary antibody or the like. If the desired antibody that reacts withthe sensitizing antigen is present in the culture supernatant, thesecondary antibody will bind to the carrier via the antibody. Finally,the presence of the desired antibody in the culture supernatant can bedetermined by detecting secondary antibodies bound to the carrier.Hybridomas producing desired antibodies with an ability to bind to theantigen can be cloned by the limiting dilution method or the like.Antigens used for immunization as well as a substantially identicalGPR49 protein can be suitably used in this case. For example, aGPR49-expressing cell line, an extracellular domain of GPR49, or anoligopeptide comprising a partial amino acid sequence constituting thisregion may be used as the antigen.

In addition to the above-mentioned method where hybridomas are obtainedby immunizing non-human animals with an antigen, a desired antibody canbe obtained by antigen sensitization of human lymphocytes. Morespecifically, first, human lymphocytes are sensitized with the GPR49protein in vitro. Then, immunosensitized lymphocytes are fused with asuitable fusion partner. For example, human-derived myeloma cells thathave infinite division potential can be used as a fusion partner (seeJapanese Patent Application Kokoku Publication No. (JP-B) H01-59878(examined, approved Japanese patent application published foropposition)). Anti-GPR49 antibodies obtained by this method are humanantibodies that have binding activity to a GPR49 protein.

Alternatively, anti-GPR49 human antibodies can also be obtained byadministering a GPR49 protein that serves as an antigen to a transgenicanimal having a complete human antibody gene repertoire, or byimmunizing such an animal with a DNA constructed to express GPR49 in theanimal. Antibody-producing cells of the immunized animal can beimmortalized by treatment such as cell fusion with a suitable fusionpartner or Epstein-Barr virus infection. Human antibodies against theGPR49 protein can be isolated from the immortalized cells obtained inthis manner (see International Patent Publication Nos. WO 94/25585, WO93/12227, WO 92/03918, and WO 94/02602). Furthermore, cells that producean antibody having the desired reaction specificity can be cloned bycloning the immortalized cells. When a transgenic animal is used as theanimal to be immunized, the immune system of this animal recognizeshuman GPR49 as a foreign substance. Therefore, human antibodies againsthuman GPR49 can be readily obtained.

The monoclonal antibody-producing hybridomas produced in this manner canbe subcultured in a standard medium. Alternatively, the hybridomas canbe stored for long periods in liquid nitrogen.

The hybridomas can be cultured according to a standard method, and thedesired monoclonal antibody can be obtained from the culturesupernatants. Alternatively, the hybridomas can be grown byadministering them to a compatible mammal, and monoclonal antibodies canbe obtained as its ascites. The former method is suitable for obtaininghighly-pure antibodies.

In the present invention, an antibody encoded by an antibody gene clonedfrom antibody-producing cells can be used. The cloned antibody gene canbe incorporated into a suitable vector and then transfected into a hostto express the antibody. Methods for isolating an antibody gene,introducing the gene into a vector, and transforming host cells havebeen established (see for example, Vandamme, A. M. et al., Eur. J.Biochem. (1990) 192, 767-775).

For example, a cDNA encoding the variable region (V region) of ananti-GPR49 antibody can be obtained from hybridoma producing theanti-GPR49 antibody. Generally in order to obtain the cDNA, first, totalRNA is extracted from the hybridoma. For example, the following methodscan be used as methods for extracting mRNA from cells:

the guanidine ultracentrifugation method (Chirgwin, J. M. et al.,Biochemistry (1979) 18, 5294-5299); and the AGPC method (Chomczynski, P.et al., Anal. Biochem. (1987) 162, 156-159).

The extracted mRNA can be purified using an mRNA Purification Kit (GEHealthcare Bio-Sciences) or the like. Alternatively, kits for directlyextracting total mRNA from cells such as the QuickPrep mRNA PurificationKit (GE Healthcare Bio-Sciences) are also commercially available. TotalmRNA can be obtained from the hybridoma by using such kits. A cDNAencoding the antibody V region can be synthesized from the obtained mRNAusing reverse transcriptase. Any of the 15- to 30-nucleotide sequencesselected from sequences common among mouse antibody genes can be used asprimers. Specifically, a cDNA encoding the antibody V region can beobtained by using primers comprising the DNA sequences shown in SEQ IDNOs: 61 to 63. cDNAs can be synthesized using the AMV ReverseTranscriptase First-strand cDNA Synthesis Kit (SEIKAGAKU CORPORATION) orthe like. To synthesize and amplify cDNAs, the 5′-Ampli FINDER RACE Kit(manufactured by Clontech) and the 5′-RACE method using PCR (Frohman, M.A. et al., Proc. Natl. Acad. Sci. USA (1988) 85, 8998-9002; Belyaysky,A. et al., Nucleic Acids Res. (1989) 17, 2919-2932) can be used.Furthermore, in the process of such cDNA synthesis, appropriaterestriction enzyme sites, which will be described later, can beintroduced into both ends of the cDNA.

The cDNA fragment of interest is purified from the obtained PCR product,and then ligated to a vector DNA. The recombinant vector is prepared inthis manner and transformed into Escherichia coli or the like, and aftercolonies are selected, the desired recombinant vector can be preparedfrom the E. coli that formed the colonies. The nucleotide sequence ofthe cDNA can be confirmed by a known method, such as thedideoxynucleotide chain termination method.

Alternatively, in order to obtain genes encoding the antibody variableregions, a cDNA library can be used. First, a cDNA library is obtainedby synthesizing cDNAs from the mRNAs extracted from theantibody-producing cells as templates. It is convenient to use acommercially available kit for cDNA library synthesis. In practice,since the amount of mRNA obtainable from only a small number of cells isextremely minute, the yield of such mRNA from direct purification islow. Therefore, purification is usually performed after adding a carrierRNA that clearly does not contain an antibody gene. Alternatively, whena certain amount of RNA can be extracted, efficient extraction can beaccomplished by using the RNA of antibody-producing cells alone. Forexample, addition of carrier RNA may not be required when RNA isextracted from ten or more, 30 or more, or preferably 50 or moreantibody-producing cells.

The antibody genes are amplified by the PCR method using the obtainedcDNA library as a template. The primers used for amplification of theantibody genes by the PCR method are known. For example, primers forhuman antibody gene amplification can be designed based on thedisclosure of an article (J. Mol. Biol. (1991) 222, 581-597) and thelike. The nucleotide sequences of these primers vary depending on theimmunoglobulin subclass. Therefore, when a cDNA library of an unknownsubclass is used as the template, the PCR method is performedconsidering all possibilities.

More specifically, for example, for obtaining genes encoding human IgG,one may use primers capable of amplifying genes encoding γ1 to γ5 forthe heavy chain, and genes encoding the κ chain and λ chain for thelight chain. To amplify genes of the IgG variable region, generally, aprimer that anneals to the portion corresponding to the hinge region isused as the 3′-end primer. Meanwhile, a primer corresponding to eachsubclass can be used as the 5′-end primer.

PCR products obtained by the primers for gene amplification of the heavychain and light chain subclasses are made into independent libraries.Using the libraries synthesized in this manner, immunoglobulinscomprising a combination of heavy and light chains can be reconstituted.The antibodies of interest can be screened by using the GPR49-bindingactivity of the reconstituted immunoglobulins as an index.

For example, for obtaining antibodies against GPR49, it is morepreferable that the binding of the antibodies to GPR49 is specific. Forinstance, it is possible to screen for antibodies that bind to GPR49according to the following steps of:

(1) contacting GPR49 with an antibody comprising a V region encoded byan obtained cDNA;(2) detecting the binding between GPR49 and the antibody; and(3) selecting the antibody that binds to GPR49.

Methods for detecting the binding between an antibody and GPR49 areknown. Specifically, a test antibody is reacted with carrier-immobilizedGPR49, and then this is reacted with a labeled antibody that recognizesthe test antibody. If the labeled antibody on the carrier is detectedafter washing, binding of the test antibody to GPR49 is proved. Forlabeling, enzymatically active proteins such as peroxidase orβ-galactosidase or fluorescent substances such as FITC can be used. Inorder to evaluate the binding activity of the antibody, fixed samples ofGPR49-expressing cells can be used.

For an antibody screening method that uses the binding activity as anindex, a phage vector-based panning method may also be used. When theantibody genes are obtained as libraries of the heavy-chain andlight-chain subclasses as described above, phage vector-based screeningmethods are advantageous. Genes encoding variable regions of the heavyand light chains can be made into a single-chain Fv (scFv) gene bylinking the genes via suitable linker sequences. Phages expressing anscFv on their surface can be obtained by inserting a gene encoding thescFv into a phage vector. DNA encoding an scFv having the desiredbinding activity can be collected by contacting the phage with theantigen and then collecting antigen-bound phage. scFv having the desiredbinding activity can be concentrated by repeating this operation asnecessary.

A polynucleotide encoding an antibody of the present invention mayencode a full-length antibody or a portion of the antibody. “A portionof an antibody” refers to any portion of an antibody molecule.Hereinafter, the term “antibody fragment” may be used to refer to aportion of an antibody. A preferred antibody fragment of the presentinvention comprises the complementarity determination region (CDR) of anantibody. More preferably, an antibody fragment of the present inventioncomprises all of the three CDRs that constitute a variable region.

Once a cDNA encoding a V region of an objective anti-GPR49 antibody isobtained, this cDNA is digested with restriction enzymes that recognizethe restriction enzyme sites inserted to both ends of the cDNA. Apreferred restriction enzyme is an enzyme that recognizes and digests anucleotide sequence that is less likely to appear in the nucleotidesequence constituting the antibody gene. Furthermore, to insert a singlecopy of the digested fragment into a vector in a correct direction, arestriction enzyme that provides sticky ends is preferred. A cDNAencoding the anti-GPR49 antibody V region, which has been digested asdescribed above, is inserted into a suitable expression vector to obtainthe antibody expression vector. In this step, a chimeric antibody can beobtained by fusing a gene encoding the antibody constant region (Cregion) with the above-mentioned gene encoding the V region in frame.Herein, “chimeric antibody” refers to an antibody whose constant andvariable regions are derived from different origins. Therefore, inaddition to heterogeneous chimeric antibodies such as mouse-humanchimeric antibodies, human-human homogeneous chimeric antibodies arealso included in the chimeric antibodies of the present invention. Achimeric antibody expression vector can also be constructed by insertingthe V region gene into an expression vector into which a DNA encoding aconstant region has been incorporated in advance.

More specifically, for example, a restriction enzyme recognitionsequence for a restriction enzyme that digests the V-region gene can beplaced at the 5′ end of an expression vector carrying a DNA encoding adesired antibody constant region (C region). The chimeric antibodyexpression vector is constructed by digesting both genes using the samecombination of restriction enzymes, and fusing them in frame.

To produce an anti-GPR49 antibody for use in the present invention, theantibody gene can be incorporated into an expression vector so that itis expressed under the control of an expression regulatory region. Theexpression regulatory region for antibody expression includes, forexample, an enhancer or a promoter. Then, by transforming suitable hostcells with this expression vector, recombinant cells that express theDNA encoding the anti-GPR49 antibody can be obtained.

To express an antibody gene, a DNA encoding the antibody heavy chain (Hchain) and a DNA encoding the antibody light chain (L chain) can beincorporated into different expression vectors. An antibody moleculecomprising the H chain and L chain can be expressed by co-transfectingthe vectors incorporating the H chain and L chain into the same hostcell. Alternatively, DNAs encoding the H chain and L chain can beincorporated into a single expression vector to transform a host cellwith the vector (see International Patent Publication No. WO 94/11523).

Many combinations of hosts and expression vectors for transfecting anisolated antibody gene into an appropriate host to prepare the antibodyare known. Any of these expression systems can be applied to the presentinvention. For using eukaryotic cells as a host, animal cells, plantcells, or fungal cells can be used. More specifically, animal cells thatmay be used in the present invention are, for example, the followingcells:

(1) mammalian cells: CHO, COS, myeloma, baby hamster kidney (BHK), HeLa,Vero, HEK293, Ba/F3, HL-60, Jurkat, SK-HEP1 cells, or such;(2) amphibian cells: Xenopus oocytes, or such; and(3) insect cells: sf9, sf21, Tn5, or such.

In addition, as a plant cell, an antibody gene expression system usingcells derived from the Nicotiana genus such as Nicotiana tabacum isknown. Callus cultured cells can be used to transform plant cells.

Furthermore, the following cells can be used as fungal cells:

yeasts: the Saccharomyces genus such as Saccharomyces cerevisiae, andthe Pichia genus such as Pichia pastoris; andfilamentous fungi: the Aspergillus genus such as Aspergillus niger.

Alternatively, antibody gene expression systems that utilize prokaryoticcells are also known. For example, when using bacterial cells, E. colicells, Bacillus subtilis cells, and such may be utilized in the presentinvention.

In the case of mammalian cells, the antibody genes can be expressed byoperably linking the antibody gene to be expressed with an effectivecommonly used promoter, and a polyA signal on the 3′ downstream side ofthe antibody gene. An example of the promoter/enhancer includes humancytomegalovirus immediate early promoter/enhancer.

Other promoters/enhancers that can be used for antibody expressioninclude viral promoters/enhancers, or mammalian cell-derivedpromoters/enhancers such as human elongation factor 1α (HEF1α). Specificexamples of viruses whose promoters/enhancers may be used includeretrovirus, polyoma virus, adenovirus, and simian virus 40 (SV40).

When an SV40 promoter/enhancer is used, the method of Mulligan et al.(Nature (1979) 277, 108) may be utilized. An HEF1α promoter/enhancer canbe readily used for expressing a gene of interest by the method ofMizushima et al. (Nucleic Acids Res. (1990) 18, 5322).

When E. coli is used, the antibody genes can be expressed by operablylinking the gene to be expressed to a conventional useful promoter and asignal sequence for antibody secretion. Such promoters include, forexample, the lacZ promoter and the araB promoter. When the lacZ promoteris used, it is possible to use the method of Ward et al. (Nature (1989)341: 544-546; FASEB J. (1992) 6: 2422-2427). Alternatively, when thearaB promoter is used to express the gene, it is possible to use themethod of Better et al. (Science (1988) 240: 1041-1043).

When the antibodies are produced into the periplasm of E. coli, the pelBsignal sequence (Lei S. P. et al., J. Bacteriol. (1987) 169: 4379) maybe used as a signal sequence for antibody secretion. After the antibodyproduced in the periplasm is isolated, the antibody structure isrefolded by using a protein denaturant like urea or guanidinehydrochloride so that the antibody will have the desired bindingactivity.

When the antibody is produced using animal cells, it is desirable to usean antibody heavy-chain gene or light-chain gene signal sequence as thesignal sequence necessary for secreting antibody outside the cell.Alternatively the signal sequence carried by a secretory protein such asIL-3 and IL-6 can be used.

The replication origin inserted into the expression vector includes, forexample, those derived from SV40, polyoma virus, adenovirus, or bovinepapilloma virus (BPV). Furthermore, in order to amplify the gene copynumber in the host cell system, a selection marker can be inserted intothe expression vector. Specifically, the following selection markers canbe used:

aminoglycoside transferase (APH) gene;thymidine kinase (TK) gene;E. coli xanthine guanine phosphoribosyltransferase (Ecogpt) gene;dihydrofolate reductase (dhfr) gene, etc.

These expression vectors are transfected into host cells, and then, thetransformed host cells are cultured in vitro or in vivo to induceproduction of the desired antibody. The host cells are culturedaccording to known methods. For example, DMEM, MEM, RPMI1640, or IMDMcan be used as the culture medium. A serum supplement solution such asfetal calf serum (FCS) can also be used in combination.

Antibodies expressed and produced as described above can be purified byusing a single known method or a suitable combination of known methodsgenerally used for purifying proteins. Antibodies can be isolated andpurified by, for example, appropriately selecting and combining affinitycolumns such as protein A column, chromatography column, filtration,ultrafiltration, salt precipitation, dialysis, and such (Antibodies ALaboratory Manual. Ed Harlow, David Lane, Cold Spring Harbor Laboratory,1988).

In addition to the above-described host cells, transgenic animals canalso be used to produce a recombinant antibody. That is, the antibodycan be obtained from an animal into which the gene encoding the antibodyof interest is introduced. For example, the antibody gene can beconstructed as a fusion gene by inserting in frame into a gene thatencodes a protein produced specifically in milk. Goat β-casein or suchcan be used, for example, as the protein secreted in milk. DNA fragmentscontaining the fused gene inserted with the antibody gene is injectedinto a goat embryo, and then this embryo is introduced into a femalegoat. Desired antibodies can be obtained as a protein fused with themilk protein from milk produced by the transgenic goat born from theembryo-recipient goat (or progeny thereof). In addition, to increase thevolume of milk containing the desired antibody produced by thetransgenic goat, hormones can be used on the transgenic goat asnecessary (Ebert, K. M. et all, Bio/Technology (1994) 12, 699-702).

Non-human animal antibody-derived C regions can be used for the Cregions of a recombinant antibody of the present invention. For example,Cγ1, Cγ2a, Cγ2b, Cγ3, Cμ, Cδ, Cα1, Cα2, and Cε can be used for the mouseantibody H chain C region, and Cκ and Cλ can be used for the L chain Cregion. In addition to mouse antibodies, antibodies of rats, rabbits,goats, sheep, camels, monkeys, and such can be used as animalantibodies. Their sequences are known. Furthermore, the C region can bemodified to improve the stability of the antibodies or their production.

In the present invention, when antibodies are administered to humans,recombinant antibodies that have been artificially modified for thepurpose of reducing xenoantigenicity against humans, or the like can beused. Examples of the recombinant antibodies include chimeric antibodiesand humanized antibodies. These modified antibodies can be producedusing known methods.

A chimeric antibody is an antibody whose variable regions and constantregions of different origins are linked. For example, an antibodycomprising the heavy chain and light chain variable regions of a mouseantibody and the heavy chain and light chain constant regions of a humanantibody is a mouse-human heterogeneous chimeric antibody. A recombinantvector expressing a chimeric antibody can be prepared by linking a DNAencoding a mouse antibody variable region to a DNA encoding a humanantibody constant region, and then inserting it into an expressionvector. The recombinant cells that have been transformed with the vectorare cultured, and the integrated DNA is expressed to obtain the chimericantibody produced in the culture. Human antibody C regions are used forthe C regions of chimeric antibodies and humanized antibodies.

For example, Cγ1, Cγ2, Cγ3, Cγ4, Cμ, Cδ, Cα1, Cα2, and Cε can be used asan H chain C region. Cκ and Cλ, can be used as an L chain C region. Theamino acid sequences of these C regions and the nucleotide sequencesencoding them are known. Furthermore, the human antibody C regions canbe modified to improve the stability of an antibody itself or productionthereof.

Generally, a chimeric antibody is composed of V regions of an antibodyderived from a non-human animal and C regions derived from a humanantibody. On the other hand, a humanized antibody consists of thecomplementarity determining region (CDR) of an antibody derived from anon-human animal, and the framework region (FR) and C region derivedfrom a human antibody. Since the antigenicity of a humanized antibody inhuman body is reduced, a humanized antibody is useful as an activeingredient for therapeutic agents of the present invention.

The antibody variable region is generally composed of threecomplementarity determining regions (CDRs) separated by four frameworkregions (FRs). CDR is a region that substantially determines the bindingspecificity of an antibody. The amino acid sequences of CDRs are highlydiverse. On the other hand, the FR-constituting amino acid sequences areoften highly homologous even among antibodies with different bindingspecificities. Therefore, generally, the binding specificity of acertain antibody can be introduced to another antibody by CDR grafting.

A humanized antibody is also called a reshaped human antibody.Specifically, humanized antibodies prepared by grafting the CDR of anon-human animal antibody such as a mouse antibody to a human antibodyand such are known. Common genetic engineering techniques for obtaininghumanized antibodies are also known.

Specifically, for example, overlap extension PCR is known as a methodfor grafting a mouse antibody CDR to a human FR. In overlap extensionPCR, a nucleotide sequence encoding a mouse antibody CDR to be graftedis added to primers for synthesizing a human antibody FR. Primers areprepared for each of the four FRs. It is generally considered that whengrafting a mouse CDR to a human FR, selecting a human FR that is highlyhomologous to a mouse FR is advantageous for maintaining the CDRfunction. That is, it is generally preferable to use a human FRcomprising an amino acid sequence highly homologous to the amino acidsequence of the FR adjacent to the mouse CDR to be grafted.

Nucleotide sequences to be ligated are designed so that they will beconnected to each other in frame. Human FRs are individually synthesizedusing the respective primers. As a result, products in which the mouseCDR-encoding DNA is attached to the individual FR-encoding DNAs areobtained. Nucleotide sequences encoding the mouse CDR of each productare designed so that they overlap with each other. Then, complementarystrand synthesis reaction is conducted to anneal the overlapping CDRregions of the products synthesized using a human antibody gene astemplate. Human FRs are ligated via the mouse CDR sequences by thisreaction.

The full length V region gene, in which three CDRs and four FRs areultimately ligated, is amplified using primers that anneal to its 5′- or3′-end, which are added with suitable restriction enzyme recognitionsequences. An expression vector for humanized antibody can be producedby inserting the DNA obtained as described above and a DNA that encodesa human antibody C region into an expression vector so that they willligate in frame. After the vector is transfected into a host toestablish recombinant cells, the recombinant cells are cultured, and theDNA encoding the humanized antibody is expressed to produce thehumanized antibody in the cell culture (see, European Patent PublicationNo. EP 239400 and International Patent Publication No. WO 96/02576).

By qualitatively or quantitatively measuring and evaluating theantigen-binding activity of the humanized antibody produced as describedabove, one can suitably select human antibody FRs that allow CDRs toform a favorable antigen-binding site when ligated through the CDRs.Amino acid residues in FRs may be substituted as necessary, so that theCDRs of a reshaped human antibody form an appropriate antigen-bindingsite. For example, amino acid sequence mutations can be introduced intoFRs by applying the PCR method used for grafting a mouse CDR into ahuman FR. More specifically, partial nucleotide sequence mutations canbe introduced into primers that anneal to the FR. Nucleotide sequencemutations are introduced into the FRs synthesized by using such primers.Mutant FR sequences having the desired characteristics can be selectedby measuring and evaluating the activity of the amino acid-substitutedmutant antibody to bind to the antigen by the above-mentioned method(Sato, K. et al., Cancer Res. (1993) 53: 851-856).

Methods for obtaining human antibodies are also known. For example,human lymphocytes are sensitized in vitro with a desired antigen orcells expressing a desired antigen. Then, by fusing the sensitizedlymphocytes with human myeloma cells, desired human antibodies havingthe antigen-binding activity can be obtained (see JP-B H01-59878). U266or such can be used as the fusion partner human myeloma cell.

Alternatively, a desired human antibody can be obtained by using adesired antigen to immunize a transgenic animal that includes the entirerepertoire of human antibody genes (see International Patent PublicationNos. WO 93/12227, WO 92/03918, WO 94/02602, WO 94/25585, WO 96/34096,and WO 96/33735). Furthermore, techniques to obtain human antibodies bypanning a human antibody library are also known. For example, the humanantibody V region is expressed as a single-chain antibody (scFv) on thesurface of a phage using a phage display method, and phages that bind tothe antigen can be selected. By analyzing the genes of selected phages,the DNA sequences encoding the human antibody V regions that bind to theantigen can be determined. After determining the DNA sequences of scFvsthat bind to the antigen, the V region sequence is fused in frame withthe desired human antibody C region sequence, and this is inserted intoa suitable expression vector to produce an expression vector. Thisexpression vector can be transfected into suitable expression cells suchas those described above, and the gene encoding the human antibody canbe expressed to obtain the human antibodies. Such methods are alreadyknown (International Patent Publication Nos. WO 92/01047, WO 92/20791,WO 93/06213, WO 93/11236, WO 93/19172, WO 95/01438, and WO 95/15388).

Therefore, an example of preferred embodiments of the antibody used inthe present invention is an antibody comprising a human constant region.

The antibodies of the present invention are not limited to bivalentantibodies represented by IgG, but include monovalent antibodies andmultivalent antibodies represented by IgM, as long as it binds to theGPR49 protein. The multivalent antibodies of the present inventioninclude multivalent antibodies that have the same antigen binding sites,and multivalent antibodies that have partially or completely differentantigen binding sites. The antibodies of the present invention are notlimited to whole antibody molecules, but include minibodies and modifiedproducts thereof, as long as they bind to the GPR49 protein.

The minibodies comprise antibody fragments lacking portions of the wholeantibody (for example, whole IgG). The minibodies may lack portions ofantibody molecules as long as they have binding activity to GPR49antigens. Antibody fragments of the present invention preferably containeither heavy chain variable regions (VH) or light chain variable regions(VL), or both, and preferably contain CDRs. The amino acid sequences ofVH or VL may contain substitutions, deletions, additions and/orinsertions. Furthermore, the antibody fragment may also lack portions ofeither VH or VL, or both, as long as it has binding ability to GPR49antigen. In addition, the variable regions may be chimerized orhumanized. Such antibody fragments include, for example, Fab, Fab′,F(ab′)₂, and Fv. An example of a minibody includes Fab, Fab′, F(ab′)₂,Fv, scFv (single-chain Fv), diabody, and sc(Fv)₂ (single-chain (Fv)₂),scFv-Fc. Multimers of these antibodies (for example, dimers, trimers,tetramers, and polymers) are also included in the minibodies of thepresent invention.

Antibody fragments can be obtained by treating an antibody with enzymesto produce antibody fragments. Known enzymes that produce antibodyfragments are, for example, papain, pepsin, and plasmin. Alternatively,genes encoding these antibody fragments can be constructed andintroduced into expression vectors to express them in appropriate hostcells (see, for example, Co, M. S. et al., J. Immunol. (1994) 152,2968-2976; Better, M. and Horwitz, A. H., Methods in Enzymology (1989)178, 476-496; Plueckthun, A. and Skerra, A., Methods in Enzymology(1989) 178, 476-496; Lamoyi, E., Methods in Enzymology (1989) 121,652-663; Rousseaux, J. et al., Methods in Enzymology (1989) 121,663-669; and Bird, R. E. et al., TIBTECH (1991) 9, 132-137).

Digestive enzymes cleave specific sites of an antibody fragment, andyield antibody fragments with the following specific structures. Whengenetic engineering techniques are used on such enzymatically obtainedantibody fragments, any portion of the antibody can be deleted.

Papain digestion: F(ab)₂ or FabPepsin digestion: F(ab′)₂ or Fab′Plasmin digestion: Facb

Therefore, minibodies of the present invention may be antibody fragmentslacking any region, as long as they have binding affinity to GPR49.Furthermore, according to the present invention, the antibodiesdesirably maintain their effector activity, particularly in thetreatment of cell proliferative diseases such as cancer. Morespecifically, preferred minibodies of the present invention have bothbinding affinity to GPR49 and effector function. The effector functionof antibodies includes ADCC activity and CDC activity. Particularlypreferably, therapeutic antibodies of the present invention have eitherADCC activity or CDC activity, or both, as effector function.

The term “diabody” refers to a bivalent antibody fragment constructed bygene fusion (Holliger P et al., 1993, Proc. Natl. Acad. Sci. USA 90:6444-6448; EP 404,097; WO 93/11161 and others). Diabodies are dimerscomprising two polypeptide chains, where each polypeptide chainconsisting dimer comprises a VL and a VH connected with a linker. Thelinker of diabody is short enough to prevent interaction of these twodomains. Specifically, amino acid residues comprising a linker is, forexample, about five residues. Therefore, the VL and VH encoded on thesame polypeptide chain cannot form a single-chain variable regionfragment, and will form a dimer with other single-chain variable regionfragment. As a result, the diabody has two antigen binding sites.

scFv can be obtained by ligating the H chain V region and L chain Vregion of an antibody. In scFv, the H chain V region and L chain Vregion are ligated via a linker, preferably a peptide linker (Huston, J.S. et al., Proc. Natl. Acad. Sci. U.S.A., 1988, 85, 5879-5883). The Hchain V region and L chain V region of scFv may be derived from any ofthe antibodies described herein. The peptide linker for ligating the Vregions is not particularly limited. For example, any single-chainpeptide consisting of 3 to 25 residues or so can be used as the linker.More specifically, for example, peptide linkers described below or suchcan be used.

PCR methods such as those described above can be used for ligating the Vregions from both chains. For ligation of the V regions by PCR methods,first, a whole DNA or a DNA encoding a desired partial amino acidsequence selected from the following DNAs can be used as a template:

a DNA sequence encoding the H chain or the H chain V region of theantibody; anda DNA sequence encoding the L chain or the L chain V region of theantibody.

DNAs encoding the H chain and L chain V regions are individuallyamplified by PCR methods using a pair of primers that have sequencescorresponding to the sequences of both ends of the DNAs to be amplified.Then, a DNA encoding the peptide linker portion is prepared. The DNAencoding the peptide linker can also be synthesized using PCR. To the 5′end of the primers used, nucleotide sequences that can be ligated toeach of the individually synthesized V region amplification products areadded. Next, PCR reaction is carried out using each of the [H-chain Vregion DNA], [peptide linker DNA], and [L-chain V region DNA], and theprimers for assembly PCR.

The primers for assembly PCR consist of a combination of a primer thatanneals to the 5′ end of the [H chain V region DNA] and a primer thatanneals to the 3′ end of the [L chain V region DNA]. That is, theprimers for assembly PCR are a primer set that can amplify a DNAencoding the full-length sequence of scFv to be synthesized. On theother hand, nucleotide sequences that can be ligated to each V-regionDNA are added to the [peptide linker DNA]. These DNAs are then ligated,and the full-length scFv is finally produced as an amplification productusing the primers for assembly PCR. Once the scFv-encoding DNA isconstructed, expression vectors containing the DNA, and recombinantcells transformed with these expression vectors can be obtainedaccording to conventional methods. Furthermore, the scFvs can beobtained by culturing the resulting recombinant cells and expressing theDNA encoding scFv.

scFv-Fc is a minibody prepared by connecting an Fc region with an scFvcomprising the H chain V region and L chain V region of an antibody(Cellular & Molecular Immunology 2006; 3: 439-443). The origin of thescFv used in scFv-Fc is not particularly limited, and for example,IgM-derived scFv may be used. Furthermore, the origin of Fe is notparticularly limited, and for example, mouse IgG2 (mouse IgG2a or such),and human IgG (human IgG1 or such) may be used. Therefore, examples ofpreferred embodiments of scFv-Fc include scFv-Fc produced by ligatingthe IgM antibody scFv fragment and the mouse IgG2a CH2 (for example Cγ2)and CH3 (for example Cγ3) using the mouse IgG2a hinge region (Hγ), andscFv-Fc produced by ligating the IgM antibody scFv fragment and thehuman IgG1 CH2 and CH3 using the human IgG1 hinge region.

sc(Fv)₂ is a single-chain minibody produced by linking two units of VHand two units of VL with linkers and such (Hudson et al., 1999, JImmunol. Methods 231:177-189). sc(Fv)2 can be produced, for example, bylinking two scFv molecules.

In a preferable antibody, the two VH units and two VL units are arrangedin the order of VH, VL, VH, and VL([VH]-linker-[VL]-linker-[VH]-linker-[VL]) beginning from the N terminusof a single-chain polypeptide.

The order of the two VH units and two VL units is not limited to theabove arrangement, and they may be arranged in any order. Examples ofthe arrangements are listed below.

[VL]-linker-[VH]-linker-[VH]-linker-[VL][VH]-linker-[VL]-linker-[VL]-linker-[VH][VH]-linker-[VH]-linker-[VL]-linker-[VL][VL]-linker-[VL]-linker-[VH]-linker-[VH][VL]-linker-[VH]-linker-[VL]-linker-[VH]

The linkers to be used for linking the variable regions of an antibodycomprise arbitrary peptide linkers that can be introduced by geneticengineering, synthetic linkers, and linkers disclosed in, for example,Protein Engineering, 9(3), 299-305, 1996. Peptide linkers are preferredin the present invention. There are no limitations as to the length ofthe peptide linkers. The length can be selected accordingly by thoseskilled in the art depending on the purpose, and amino acid residuescomprising peptide linker is typically 1 to 100 amino acids, preferably3 to 50 amino acids, more preferably 5 to 30 amino acids, and even morepreferably 12 to 18 amino acids (for example, 15 amino acids).

Amino acid sequences of the peptide linkers comprise arbitrary sequencesas long as they do not inhibit the scFv binding ability. For example,such peptide linkers include:

Ser Gly-Ser Gly-Gly-Ser Ser-Gly-Gly Gly-Gly-Gly-Ser (SEQ ID NO: 53)Ser-Gly-Gly-Gly (SEQ ID NO: 54) Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 55)Ser-Gly-Gly-Gly-Gly (SEQ ID NO: 56) Gly-Gly-Gly-Gly-Gly-Ser(SEQ ID NO: 57) Ser-Gly-Gly-Gly-Gly-Gly (SEQ ID NO: 58)Gly-Gly-Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 59) Ser-Gly-Gly-Gly-Gly-Gly-Gly(SEQ ID NO: 60) (Gly-Gly-Gly-Gly-Ser (SEQ ID NO: 53))n(Ser-Gly-Gly-Gly-Gly (SEQ ID NO: 54))nwhere n is an integer of 1 or larger.

The amino acid sequences of peptide linkers can be selected accordinglyby those skilled in the art depending on the purpose. For example, “n”,which determines the length of peptide linker described above, istypically 1 to 5, preferably 1 to 3, or more preferably 1 or 2.

In an embodiment of the present invention, a particularly preferablesc(Fv)2 includes, for example, the sc(Fv)2 below.

[VH]-peptide linker (15 amino acids)-[VL]-peptide linker (15 aminoacids)-[VH]-peptide linker (15 amino acids)-[VL]

Alternatively, V regions can be crosslinked using synthetic linkers(chemical crosslinking agents). Crosslinking agents routinely used tocrosslink peptide compounds can be used in the present invention. Forexample, chemical crosslinking agents such as the following is known.These crosslinking agents are commercially available.

N-hydroxy succinimide (NHS),disuccinimidyl suberate (DSS),bis(sulfosuccinimidyl) suberate (BS³),dithiobis(succinimidyl propionate) (DSP),dithiobis(sulfosuccinimidyl propionate) (DTSSP),ethylene glycol bis(succinimidyl succinate) (EGS),ethylene glycol bis(sulfosuccinimidyl succinate) (sulfo-EGS),disuccinimidyl tartrate (DST), disulfosuccinimidyl tartrate (sulfo-DST),bis[2-(succinimidoxycarbonyloxy)ethyl]sulfone (BSOCOES),and bis[2-(sulfosuccinimidoxycarbonyloxy)ethyl]sulfone (sulfo-BSOCOES).

In general, three linkers are required to link four antibody variableregions together. The linkers to be used may be of the same type ordifferent types. In the present invention, a preferable minibody is adiabody or an sc(Fv)₂. Such a minibody can be prepared by treating anantibody with an enzyme, for example, papain or pepsin, to generateantibody fragments, or by constructing DNAs encoding those antibodyfragments and introducing them into expression vectors, followed byexpression in an appropriate host cell (see, for example, Co, M. S. etal., 1994, J. Immunol. 152, 2968-2976; Better, M. and Horwitz, A. H.,1989, Methods Enzymol. 178, 476-496; Pluckthun, A. and Skerra, A., 1989,Methods Enzymol. 178, 497-515; Lamoyi, E., 1986, Methods Enzymol. 121,652-663; Rousseaux, J. et al., 1986, Methods Enzymol. 121, 663-669;Bird, R. E. and Walker, B. W., 1991, Trends Biotechnol. 9, 132-137).

Furthermore, the antibodies of the present invention include not onlymonovalent antibodies but also multivalent antibodies. Multivalentantibodies of the present invention include multivalent antibodies whoseantigen binding sites are all the same and multivalent antibodies whoseantigen binding sites are partially or completely different.

Antibodies conjugated to various types of molecules such as polyethyleneglycol (PEG) can also be used as modified antibodies. Moreover,cytotoxic substances such as chemotherapeutic agents, toxic peptides, orradioactive chemical substances can be conjugated to the antibodies.Such modified antibodies (hereinafter referred to as antibodyconjugates) can be obtained by chemically-modifying the obtainedantibodies. Methods for modifying antibodies are already established inthis field. Furthermore, as described below, such antibodies can also beobtained in the molecular form of a bispecific antibody designed usinggenetic engineering techniques to recognize not only GPR49 proteins, butalso cytotoxic substances such as chemotherapeutic agents, toxicpeptides, and radioactive chemical substances. These antibodies are alsoincluded in the “antibodies” of the present invention.

Chemotherapeutic agents that are linked to anti-GPR49 antibodies toexert an cytotoxic activity include the following: azaribine,anastrozole, azacytidine, bleomycin, bortezomib, bryostatin-1, busulfan,camptothecin, 10-hydroxycamptothecin, carmustine, celebrex,chlorambucil, cisplatin, irinotecan, carboplatin, cladribine,cyclophosphamide, cytarabine, dacarbazine, docetaxel, dactinomycin,daunomycin glucuronide, daunorubicin, dexamethasone, diethylstilbestrol,doxorubicin, doxorubicin glucuronide, epirubicin, ethinyl estradiol,estramustine, etoposide, etoposide glucuronide, floxuridine,fludarabine, flutamide, fluorouracil, fluoxymesterone, gemcitabine,hydroxyprogesterone caproate, hydroxyurea, idarubicin, Ifosfamide,leucovorin, lomustine, mechlorethamine, medroxyprogesterone acetate,megestrol acetate, melphalan, mercaptopurine, methotrexate,mitoxantrone, mithramycin, mitomycin, mitotane, phenylbutyrate,prednisone, procarbazine, paclitaxel, pentostatin, semustine,streptozocin, tamoxifen, taxanes, taxol, testosterone propionate,thalidomide, thioguanine, thiotepa, teniposide, topotecan, uracilmustard, vinblastine, vinorelbine, and vincristine.

In the present invention, preferred chemotherapeutic agents arelow-molecular-weight chemotherapeutic agents. Low-molecular-weightchemotherapeutic agents are unlikely to interfere with antibody functioneven after binding to antibodies. In the present invention,low-molecular-weight chemotherapeutic agents usually have a molecularweight of 100 to 2,000, preferably 200 to 1,000. The chemotherapeuticagents exemplified herein are all low-molecular-weight chemotherapeuticagents. The chemotherapeutic agents of the present invention includeprodrugs that are converted to active chemotherapeutic agents in vivo.Prodrug activations may be enzymatic conversion or non-enzymaticconversion.

Furthermore, the antibodies can be modified using toxic peptides.Examples of toxic peptides include the following: Diphtheria toxin AChain (Langone J. J., et al., Methods in Enzymology, 93, 307-308, 1983),Pseudomonas Exotoxin (Nature Medicine, 2, 350-353, 1996), Ricin A Chain(Fulton R. J., et al., J. Biol. Chem., 261, 5314-5319, 1986; Sivam G.,et al., Cancer Res., 47, 3169-3173, 1987; Cumber A. J. et al., J.Immunol. Methods, 135, 15-24, 1990; Wawrzynczak E. J., et al., CancerRes., 50, 7519-7562, 1990; Gheeite V., et al., J. Immunol. Methods, 142,223-230, 1991), Deglicosylated Ricin A Chain (Thorpe P. E., et al.,Cancer Res., 47, 5924-5931, 1987), Abrin A Chain (Wawrzynczak E. J., etal., Br. J. Cancer, 66, 361-366, 1992; Wawrzynczak E. J., et al., CancerRes., 50, 7519-7562, 1990; Sivam G., et al., Cancer Res., 47, 3169-3173,1987; Thorpe P. E., et al., Cancer Res., 47, 5924-5931, 1987), Gelonin(Sivam G., et al., Cancer Res., 47, 3169-3173, 1987; Cumber A. J. etal., J. Immunol. Methods, 135, 15-24, 1990; Wawrzynczak E. J., et al.,Cancer Res., 50, 7519-7562, 1990; Bolognesi A., et al., Clin. exp.Immunol., 89, 341-346, 1992), PAP-s; Pokeweed anti-viral protein fromseeds (Bolognesi A., et al., Clin. exp. Immunol., 89, 341-346, 1992),Briodin (Bolognesi A., et al., Clin. exp. Immunol., 89, 341-346, 1992),Saporin (Bolognesi A., et al., Clin. exp. Immunol., 89, 341-346, 1992),Momordin (Cumber A. J., et al., J. Immunol. Methods, 135, 15-24, 1990;Wawrzynczak E. J., et al., Cancer Res., 50, 7519-7562, 1990; BolognesiA., et al., Clin. exp. Immunol., 89, 341-346, 1992), Momorcochin(Bolognesi A., et al., Clin. exp. Immunol., 89, 341-346, 1992), Dianthin32 (Bolognesi A., et al., Clin. exp. Immunol., 89, 341-346, 1992),Dianthin 30 (Stirpe F., Barbieri L., FEBS letter 195, 1-8, 1986),Modeccin (Stirpe F., Barbieri L., FEBS letter 195, 1-8, 1986), Viscumin(Stirpe F., Barbieri L., FEBS letter 195, 1-8, 1986), Volkesin (StirpeF., Barbieri L., FEBS letter 195, 1-8, 1986), Dodecandrin (Stirpe F.,Barbieri L., FEBS letter 195, 1-8, 1986), Tritin (Stirpe F., BarbieriL., FEBS letter 195, 1-8, 1986), Luffin (Stirpe F., Barbieri L., FEBSletter 195, 1-8, 1986), or Trichokirin (Casellas P., et al., Eur. J.Biochem. 176, 581-588, 1988; Bolognesi A., et al., Clin. exp. Immunol.,89, 341-346, 1992).

A radioactive chemical substance in the present invention refers to achemical substance comprising a radioisotope. The radioisotope is notparticularly limited, and any radioisotope may be used, but for example,³²P, ¹⁴C, ¹²⁵I, ³H, ¹³¹I, ¹⁸⁶Re, ¹⁸⁸Re, and such may be used. In anotherembodiment one, two, or more of the low-molecular-weightchemotherapeutic agents and toxic peptides can be combined and used forantibody modification. The bonding between an anti-GPR49 antibody andthe above-mentioned low-molecular-weight chemotherapeutic agent may becovalent bonding or non-covalent bonding. Methods for producingantibodies bound to these chemotherapeutic agents are known.

Furthermore, proteinaceous pharmaceutical agents or toxins can be boundto antibodies by genetic engineering techniques. Specifically, forexample, it is possible to construct a recombinant vector by fusing aDNA encoding the above-mentioned toxic peptide with a DNA encoding ananti-GPR49 antibody in frame, and inserting this into an expressionvector. This vector is transfected into suitable host cells, theobtained transformed cells are cultured, and the incorporated DNA isexpressed. Thus an anti-GPR49 antibody conjugated to the toxic peptidecan be obtained as a fusion protein. When obtaining an antibody as afusion protein, the proteinaceous pharmaceutical agent or toxin isgenerally positioned at the C-terminus of the antibody. A peptide linkercan be positioned between the antibody and the proteinaceouspharmaceutical agent or toxin.

Furthermore, the antibody of the present invention may be a bispecificantibody. A bispecific antibody refers to an antibody that carriesvariable regions that recognize different epitopes within the sameantibody molecule. In the present invention, the bispecific antibody mayhave antigen-binding sites that recognize different epitopes on a GPR49molecule. Two molecules of such a bispecific antibody can bind to onemolecule of GPR49. As a result, stronger cytotoxic action can beexpected.

Alternatively, the bispecific antibody may be an antibody in which oneantigen-binding site recognizes GPR49, and the other antigen-bindingsite recognizes a cytotoxic substance. Specifically, cytotoxicsubstances include chemotherapeutic agents, toxic peptides, andradioactive chemical substances. Such a bispecific antibody binds toGPR49-expressing cells, and at the same time, captures cytotoxicsubstances. This enables the cytotoxic substances to directly act onGPR49-expressing cells. Therefore, bispecific antibodies that recognizecytotoxic substance can specifically injure tumor cells and suppresstumor cell proliferation.

Furthermore, in the present invention, bispecific antibodies thatrecognize antigens other than GPR49 may be combined. For example, it ispossible to combine bispecific antibodies that recognize non-GPR49specifically expressed on the surface of target cancer cells like GPR49.

Methods for producing bispecific antibodies are known. For example, twotypes of antibodies recognizing different antigens may be linked toprepare a bispecific antibody. The antibodies to be linked may be halfmolecules each having an H chain or an L chain, or may be quartermolecules consisting of only an H chain. Alternatively, bispecificantibody-producing fused cells can be prepared by fusing hybridomasproducing different monoclonal antibodies. Bispecific antibodies canalso be prepared by genetic engineering techniques.

Known means can be used to measure the antigen-binding activity of theantibodies (Antibodies A Laboratory Manual. Ed Harlow, David Lane, ColdSpring Harbor Laboratory, 1988). For example, an enzyme linkedimmunosorbent assay (ELISA), an enzyme immunoassay (EIA), aradioimmunoassay (RIA), or a fluoroimmunoassay can be used.

The antibodies of the present invention may be antibodies with modifiedsugar chains. It is known that the cytotoxic activity of an antibody canbe increased by modifying its sugar chain. Known antibodies havingmodified sugar chains include the following:

glycosylated antibodies (for example, WO 99/54342);antibodies with defucosylated sugar chains (for example, WO 00/61739 andWO 02/31140);antibodies having a sugar chain with bisecting GlcNAc (for example, WO02/79255); etc.

Whether or not an antibody has cell proliferation-inhibiting activityagainst cells that express GPR49 proteins can be measured by a methodknown to those skilled in the art. For example, cellproliferation-inhibiting activity can be measured by culturing cellsthat expresses GRP49 proteins in the presence or absence (or in thepresence of a negative control antibody) of a target antibody, and thencounting the number of viable cells. As long as cell proliferation isinhibited, the inhibition ratio is not particularly limited, butpreferred examples include the number of viable cells in the presence ofthe target antibody which is 90% or less, 70% or less, 50% or less, orsuch compared to the number of viable cells in its absence. Cells thatexpress GRP49 proteins are not particularly limited, but include cellstransformed with a gene encoding a GPR49 protein and cells of gastriccancer, colon cancer, hepatocellular carcinoma, lung cancer, ovariancancer, and glioma.

When using antibodies of the present invention for therapeutic purposes,the antibodies are preferably antibodies having cytotoxic activity.

In the present invention, the cytotoxic activity includes, for example,antibody-dependent cell-mediated cytotoxicity (ADCC) activity andcomplement-dependent cytotoxicity (CDC) activity. In the presentinvention, CDC activity refers to complement system-mediated cytotoxicactivity. Meanwhile, ADCC activity refers to the activity of damaging atarget cell when a specific antibody attaches to its cell surfaceantigen. An Fcγ receptor-retaining cell (immunocyte or such) binds tothe Fc portion of the antibody via the Fcγ receptor and the target cellis damaged.

Whether or not an anti-GPR49 antibody has ADCC activity or CDC activitycan be determined by known methods (for example, Current protocols inImmunology, Chapter 7. Immunologic studies in humans, Editor, John E,Coligan et al., John Wiley & Sons, Inc., (1993), etc.).

Specifically, first, effector cells, complement solution, and targetcells are prepared.

(1) Preparation of Effector Cells

Spleen is removed from a CBA/N mouse or the like, and spleen cells areisolated in RPMI1640 medium (manufactured by Invitrogen). After washingwith the same medium containing 10% fetal bovine serum (FBS,manufactured by HyClone), effector cells with a cell concentrationadjusted to 5×10⁶ cells/mL were prepared.

(2) Preparation of Complement Solution

Baby Rabbit Complement (manufactured by CEDARLANE) is diluted 10-foldwith a culture medium (manufactured by Invitrogen) containing 10% FBS toprepare a complement solution.

(3) Preparation of Target Cells

GPR49 protein-expressing cells can be radioactively labeled byincubating the target cells with 0.2 mCi of sodium chromate-⁵¹Cr(manufactured by GE Healthcare Bio-Sciences) in a DMEM medium containing10% FBS for one hour at 37° C. For GPR49 protein-expressing cells, onemay use cells transformed with a gene encoding the GPR49 protein, cellsfrom stomach cancer, colon cancer, liver cell cancer, lung cancer, orovary cancer, glioma cells, or such. After radioactive labeling, cellsare washed three times with RPMI1640 medium containing 10% FBS, and thetarget cells can be prepared by adjusting the cell concentration to2×10⁵ cells/mL.

ADCC activity and CDC activity can be measured by the method describedbelow. In the case of ADCC activity measurement, 50 μL of the targetcells and 50 μL of the anti-GPR49 antibody are each added to a 96-wellU-bottom plate (manufactured by Becton Dickinson), and reacted for 15minutes on ice. Thereafter, 100 μL of effector cells are added andincubated in a carbon dioxide incubator for four hours. The finalconcentration of the antibody is adjusted to 0 or 10 μg/mL. Afterincubation, 100 μL of the supernatant is collected, and radioactivity ismeasured with a gamma counter (COBRAII AUTO-GAMMA, MODEL D5005,manufactured by Packard Instrument Company). The cytotoxic activity (%)can be calculated using values obtained from the equation(A−C)/(B−C)×100. A represents the radioactivity (cpm) in each sample, Brepresents the radioactivity (cpm) in a sample where 1% NP-40(manufactured by Nacalai Tesque) has been added, and C represents theradioactivity (cpm) of a sample containing the target cells alone.

Meanwhile, in the case of CDC activity measurement, 50 μL of target celland 50 μL of an anti-GPR49 antibody are added to a 96-well flat-bottomplate (manufactured by Becton Dickinson), and reacted for 15 minutes onice. Thereafter, 100 μL of the complement solution is added, andincubated in a carbon dioxide incubator for four hours. The finalconcentration of the antibody is adjusted to 0 or 3 μg/mL. Afterincubation, 100 μL of supernatant is collected, and the radioactivity ismeasured with a gamma counter. The cytotoxic activity can be calculatedin the same way as in the ADCC activity determination.

On the other hand, in the case of measuring the cytotoxic activity of anantibody conjugate, 50 μL of target cell and 50 μL of an anti-GPR49antibody conjugate are added to a 96-well flat-bottom plate(manufactured by Becton Dickinson), and reacted for 15 minutes on ice.This is then incubated in a carbon dioxide incubator for one to fourhours. The final concentration of the antibody is adjusted to 0 or 3μg/mL. After incubation, 100 μL of supernatant is collected, and theradioactivity is measured with a gamma counter. The cytotoxic activitycan be calculated in the same way as in the ADCC activity determination.An example of other embodiments of an antibody used in the presentinvention is an antibody having an internalizing activity. In thepresent invention, “antibody having an internalizing activity” denotesantibody that is transported into a cell (into a cytoplasm, vesicles,other organelles, and such) upon binding to a cell surface GPR49.

Whether or not an antibody has an internalizing activity can beconfirmed using methods known to those skilled in the art. For example,the internalizing activity can be confirmed by the method of contactinga label-conjugated anti-GPR49 antibody with GPR49-expressing cells andconfirming whether or not the labeled substance was incorporated intothe cells, or by the method of contacting a cytotoxicsubstance-conjugated anti-GPR49 antibody with GPR49-expressing cells andconfirming whether or not cell death has been induced in theGPR49-expressing cells. More specifically, whether or not an antibodyhas an internalizing activity can be confirmed by the method describedin the examples provided below.

For example, antibodies having an internalizing activity can be used aspharmaceutical compositions for anticancer agents and such byconjugating them with the above-mentioned cytotoxic substances.

Any GPR49-recognizing antibody can be used as the antibody of thepresent invention. For example, preferred antibodies include theantibodies of (1) to (20) below. These antibodies may be, for example,full-length antibodies, minibodies, animal antibodies, chimericantibodies, humanized antibodies, or human antibodies:

(1) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 5 as CDR1, the amino acid sequence of SEQ ID NO: 6 as CDR2,and the amino acid sequence of SEQ ID NO: 7 as CDR3;(2) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 10 as CDR1, the amino acid sequence of SEQ ID NO: 11 as CDR2,and the amino acid sequence of SEQ ID NO: 12 as CDR3;(3) an antibody comprising the H chain of (1) and the L chain of (2);(4) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 15 as CDR1, the amino acid sequence of SEQ ID NO: 16 as CDR2,and the amino acid sequence of SEQ ID NO: 17 as CDR3;(5) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 20 as CDR1, the amino acid sequence of SEQ ID NO: 21 as CDR2,and the amino acid sequence of SEQ ID NO: 22 as CDR3;(6) an antibody comprising the H chain of (4) and the L chain of (5);(7) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 25 as CDR1, the amino acid sequence of SEQ ID NO: 26 as CDR2,and the amino acid sequence of SEQ ID NO: 27 as CDR3;(8) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 31 as CDR2,and the amino acid sequence of SEQ ID NO: 32 as CDR3;(9) an antibody comprising the H chain of (7) and the L chain of (8);(10) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 35 as CDR1, the amino acid sequence of SEQ ID NO: 36 as CDR2,and the amino acid sequence of SEQ ID NO: 37 as CDR3;(11) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 40 as CDR1, the amino acid sequence of SEQ ID NO: 41 as CDR2,and the amino acid sequence of SEQ ID NO: 42 as CDR3;(12) an antibody comprising the H chain of (10) and the L chain of (11);(13) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 45 as CDR1, the amino acid sequence of SEQ ID NO: 46 as CDR2,and the amino acid sequence of SEQ ID NO: 47 as CDR3;(14) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 50 as CDR1, the amino acid sequence of SEQ ID NO: 51 as CDR2,and the amino acid sequence of SEQ ID NO: 52 as CDR3;(15) an antibody comprising the H chain of (13) and the L chain of (14);(16) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 66 as CDR1, the amino acid sequence of SEQ ID NO: 67 as CDR2,and the amino acid sequence of SEQ ID NO: 68 as CDR3;(17) an antibody comprising an L chain having the amino acid sequence ofSEQ ID NO: 71 as CDR1, the amino acid sequence of SEQ ID NO: 72 as CDR2,and the amino acid sequence of SEQ ID NO: 73 as CDR3;(18) an antibody comprising the H chain of (16) and the L chain of (17);(19) an antibody having one or more amino acid substitutions, deletions,additions, and/or insertions in the antibody of any of (1) to (18),which has equivalent activity as the antibody of any of (1) to (18);(20) an antibody that binds to the same epitope as the GPR49 proteinepitope bound by the antibody of any of (1) to (18).

In the present invention, “have equivalent activity to an antibody” ofthe present invention means having equivalent binding activity to GPR49and/or having equivalent cytotoxic activity to GPR49-expressing cells.

Methods for preparing polypeptides functionally equivalent to a certainpolypeptide are well known to those skilled in the art, and includemethods of introducing mutations into polypeptides. For example, thoseskilled in the art can prepare an antibody functionally equivalent tothe antibodies of the present invention by introducing appropriatemutations into the antibody using site-directed mutagenesis(Hashimoto-Gotoh, T. et al., Gene (1995) 152: 271-275; Zoller, M J, andSmith, M. Methods Enzymol. (1983) 100: 468-500; Kramer, W. et al.,Nucleic Acids Res. (1984) 12: 9441-9456; Kramer, W. and Fritz H J,Methods Enzymol. (1987) 154: 350-367; Kunkel, T A, Proc. Natl. Acad.Sci. USA. (1985) 82: 488-492; Kunkel, Methods Enzymol. (1988) 85:2763-2766), or such. Amino acid mutations may occur naturally. Thus, thepresent invention also comprises antibodies functionally equivalent tothe antibodies of the present invention and comprising the amino acidsequences of these antibodies, in which one or more amino acids ismutated.

Generally, the number of amino acids that are mutated in such a mutantis 50 amino acids or less, preferably 30 or less, more preferably 10 orless (for example, five amino acids or less).

Amino acid residues having similar side chain properties are preferablymutated. For example, the following classification is established basedon amino acid side chain properties:

hydrophobic amino acids (A, I, L, M, F, P, W, Y, and V);hydrophilic amino acids (R, D, N, C, E, Q, G, H, K, S, and T);amino acids comprising the following side chains: aliphatic side chains(G, A, L, I, and P);hydroxyl-containing side chains (S, T, and Y);sulfur-containing side chains (C and M);carboxylic acid- and amide-containing side chains (D, N, E, and Q);basic side chains (R, K, and H);aromatic ring-containing side chains (H, F, Y, and W)(amino acids are represented by one-letter codes in parentheses).

A polypeptide comprising a modified amino acid sequence, in which one ormore amino acid residues is deleted, added, and/or replaced with otheramino acids, is known to retain its original biological activity (Mark,D. F. et al., Proc. Natl. Acad. Sci. USA 81, 5662-5666 (1984); Zoller,M. J. & Smith, M., Nucleic Acids Research 10, 6487-6500 (1982); Wang, A.et al., Science 224, 1431-1433; Dalbadie-McFarland, G. et al., Proc.Natl. Acad. Sci. USA 79, 6409-6413 (1982)). That is, generally in anamino acid sequence constituting a certain polypeptide, the activity ofthe polypeptide is highly likely to be maintained when amino acidsclassified into the same group are mutually substituted. In the presentinvention, the above-mentioned substitution between amino acids withinthe same amino acid group is referred to as conservative substitution.

The present invention also provides antibodies that bind to the sameepitope as the anti-GPR49 antibodies disclosed in the present inventionbind. More specifically, the present invention relates to antibodiesthat recognize the same epitope recognized by 2J18, 2L13, 2L36, 2U1E,and 2U2E, and uses of those antibodies. Such antibodies can be obtained,for example, by the following method.

Whether a test antibody shares an epitope of a certain antibody can beconfirmed by checking whether the two antibodies compete for the sameepitope. Competition between antibodies can be detected by across-blocking assay and such. For example, competitive ELISA is apreferred cross-blocking assay.

Specifically, in a cross-blocking assay, the microtiter plate wellscoated with the GPR49 protein are pre-incubated with or without acandidate competitive antibody, and an anti-GPR49 antibody of thepresent invention is then added. The amount of the anti-GPR49 antibodyof the present invention bound to the GPR49 protein in the wellsindirectly correlates with the binding ability of the candidatecompetitive antibody (test antibody) that competes for the same epitopebinding. More specifically, the greater the affinity the test antibodyhas for the same epitope, the lower the amount of the anti-GPR49antibody of the present invention binding to the GPR49 protein-coatedwells, and at the same time, the higher the amount of the test antibodybinding to the GPR49 protein-coated wells.

The amount of antibody that binds to the wells can be measured easily bylabeling the antibody in advance. For example, a biotin-labeled antibodycan be measured using an avidin-peroxidase conjugate and suitablesubstrate. Cross-blocking assays using enzyme labels such as peroxidaseare called competitive ELISA assay, in particular. The antibody can belabeled with other detectable or measurable labeling substances. Morespecifically, radiolabels or fluorescent labels are known.

Furthermore, when the test antibody comprises a constant region derivedfrom a species different from that of the anti-GPR49 antibody of thepresent invention, either one of antibodies bound to the wells can bemeasured using a labeled antibody that recognizes any one of theconstant regions. Alternatively, if the antibodies are derived from thesame species but belong to different classes, the antibodies bound tothe wells can be measured using antibodies that distinguish individualclasses.

If a candidate competitive antibody can block binding of the anti-GPR49antibody by at least 20%, preferably by at least 30%, and morepreferably by at least 50%, as compared to the binding activity obtainedin a control experiment performed in the absence of the candidatecompetitive antibody, the candidate competitive antibody is either anantibody that binds substantially to the same epitope or one thatcompetes for binding to the same epitope as an anti-GPR49 antibody ofthe present invention.

An example of an epitope recognized by the antibody of any of theabove-mentioned (4) to (6) includes the region from amino acid position517 to amino acid position 537 in the human GPR49 protein (SEQ ID NO:1). On the other hand, an example of an epitope recognized by theantibody of any of the above-mentioned (16) to (18) includes the regionfrom amino acid position 510 to amino acid position 529 in the humanGPR49 protein (SEQ ID NO: 1).

Pharmaceutical Compositions

In another aspect, the present invention provides pharmaceuticalcompositions comprising an antibody that binds to a GPR49 protein as anactive ingredient. In addition, the present invention relates to acell-growth inhibitor, in particular an anticancer agent, comprising anantibody that binds to a GPR49 protein as an active ingredient.Cell-growth inhibitors and anticancer agents of the present inventionare preferably administered to a subject affected by cancer, or to asubject who is likely to be affected by cancer. Since GPR49 expressionlevel is very low in normal cells other than brain, but at the same timeupregulated in cancer cells, it is considered that administration of ananti-GPR49 antibody can yield cancer cell-specific cytotoxic activity.

The anti-GPR49 antibodies used in the pharmaceutical composition of thepresent invention (for example, anticancer agent) are not particularlylimited and may be any anti-GPR49 antibodies, and examples include theabove-described anti-GPR49 antibodies.

GPR49 protein has been found to be cleaved and divided into 60-kDa and40-kDa fragments, and the N-terminal side 60-kDa fragment has been foundto be secreted to the outside of the cells after cleavage. Therefore,the anti-GPR49 antibodies used in the pharmaceutical composition of thepresent invention are not particularly limited, but preferably recognizethe C-terminal side 40-kDa fragment. Examples of the C-terminal side40-kDa fragment include fragments comprising the amino acid sequencefrom amino acid position 510 to 907 in SEQ ID NO: 1, and such.

Within the amino acid sequence from amino acid position 510 to 907 inSEQ ID NO: 1, the extracellular regions are the region from amino acidposition 510 to 556, the region from amino acid position 615 to 637, theregion from amino acid position 704 to 722, and the region from aminoacid position 792 to 800. Therefore, without particular limitation,antibodies recognizing these regions are particularly useful aspharmaceutical compositions.

In the present invention, the phrase “comprising an antibody that bindsto GPR49 as an active ingredient” means comprising an anti-GPR49antibody as the main active ingredient, and does not limit theanti-GPR49 antibody content rate.

When cancer is a target disease of the pharmaceutical composition of thepresent invention, the target cancer is not particularly limited, but ispreferably gastric cancer, colon cancer, hepatocellular carcinoma, lungcancer, prostate cancer, ovarian cancer, Ewing's sarcoma, and glioma(for example glioblastoma), and is particularly preferably gastriccancer. The cancers may be primary lesion or metastatic foci.

The pharmaceutical compositions of the present invention can beadministered orally or parenterally to a patient. Preferably, theadministration is parenteral administration. Specifically, theadministration method is, for example, administration by injection,transnasal administration, transpulmonary administration, or transdermaladministration. Examples of administration by injection include systemicand local administrations of a pharmaceutical composition of the presentinvention by intravenous injection, intramuscular injection,intraperitoneal injection, subcutaneous injection, or such. A suitableadministration method may be selected according to the age of thepatient and symptoms. The dosage may be selected, for example, withinthe range of 0.0001 mg to 1,000 mg per kg body weight in eachadministration. Alternatively, for example, the dosage for each patientmay be selected within the range of 0.001 to 100,000 mg/body. However,the pharmaceutical composition of the present invention is not limitedto these doses.

The pharmaceutical compositions of the present invention can beformulated according to conventional methods (for example, Remington'sPharmaceutical Science, latest edition, Mark Publishing Company, Easton,U.S.A.), and may also contain pharmaceutically acceptable carriers andadditives. Examples include, but are not limited to, surfactants,excipients, coloring agents, flavoring agents, preservatives,stabilizers, buffers, suspension agents, isotonic agents, binders,disintegrants, lubricants, fluidity promoting agents, and corrigents,and other commonly used carriers can be suitably used. Specific examplesof the carriers include light anhydrous silicic acid, lactose,crystalline cellulose, mannitol, starch, carmellose calcium, carmellosesodium, hydroxypropyl cellulose, hydroxypropyl methylcellulose,polyvinylacetal diethylaminoacetate, polyvinylpyrrolidone, gelatin,medium-chain triglyceride, polyoxyethylene hardened castor oil 60,saccharose, carboxymethyl cellulose, corn starch, inorganic salt, andsuch.

The present invention also provides methods for inducing damages inGPR49-expressing cells and methods for suppressing cell proliferation bycontacting GPR49-expressing cells with antibodies that bind to the GPR49protein.

Antibodies used in the methods of the present invention are notparticularly limited, but for example, the antibodies described abovemay be used. Cells that are bound by the anti-GPR49 antibodies are notparticularly limited as long as the cells are expressing GPR49.Preferred GPR49-expressing cells of the present invention are cancercells. More preferably, the cells are gastric cancer cells, colon cancercells, liver cancer cells, lung cancer cells, prostate cancer cells, orovarian cancer cells, Ewing's sarcoma, or glioma cells (for example,glioblastoma cells). Methods of the present invention can be applied toboth primary lesion and metastatic foci of these cancers. More preferredcancer cells are primary gastric cancer and metastatic gastric cancer.

In the present invention “contacting” is accomplished, for example, byadding antibodies to a culture solution of GPR49-expressing cellscultured in vitro. Furthermore, “contacting” in the present invention isalso carried out by administering to a non-human animal to which aGPR49-expressing cell has been transplanted into the body, or to ananimal carrying cancer cells which endogenously express GPR49.

The following method is preferably used as a method for evaluating ormeasuring cell damage induced on GPR49-expressing cells by contactingthe cells with an anti-GPR49 antibody. A method for evaluating ormeasuring the cytotoxic activity in vitro include methods for measuringthe above-mentioned antibody-dependent cell-mediated cytotoxicity (ADCC)activity, complement-dependent cytotoxicity (CDC) activity, and such.Whether or not an anti-GPR49 antibody has ADCC activity or CDC activitycan be measured by known methods (for example, Current protocols inImmunology, Chapter 7. Immunologic studies in humans, Editor, John E.Coligan et al., John Wiley & Sons, Inc., (1993) and the like). Foractivity measurements, a binding antibody having the same isotype asanti-GPR49 antibody but not having the cytotoxic activities can be usedas a control antibody in the same manner as the anti-GPR49 antibody, andactivity can be confirmed when the anti-GPR49 antibody shows a strongercytotoxic activity than the control antibody.

An antibody isotype is defined by the amino acid sequence of H chainconstant region in the antibody. The isotype of an antibody isultimately determined in vivo by class switching that arises fromgenetic recombinations in chromosomes which occur during maturation ofantibody-producing B-cells. Difference in isotype is reflected in thedifference of physiological and pathological functions of antibodies.Specifically, for example, the intensity of cytotoxic activity is knownto be influenced by antibody isotype as well as the expression level ofthe antigen. Therefore, when measuring the above-described cytotoxicactivity, an antibody of the same isotype as the test antibody ispreferably used as the control.

Furthermore, to evaluate or measure cytotoxic activity in vivo, forexample, GPR49-expressing cancer cells are intradermally orsubcutaneously transplanted to a non-human animal subject, and then atest antibody is intravenously or intraperitoneally administered dailyor at intervals of few days, starting from the day of transplantation orthe following day. Cytotoxic activity can be determined by dailymeasurement of tumor size. In a manner similar to the evaluation invitro, cytotoxic activity can be determined by administering a controlantibody having the same isotype, and observing that the tumor size inthe anti-GPR49 antibody-administered group is significantly smaller thanthat of control antibody-administered group. When mouse is used as thenon-human animal subject, it is preferable to use a nude (nu/nu) mousewhose thymus has been made genetically defective so that its Tlymphocyte function is lost. The use of such a mouse can eliminate theinvolvement of T lymphocytes in the test animals when evaluating ormeasuring the cytotoxic activity of the administered antibody.

Furthermore, the present invention provides methods for diagnosingcancer comprising detecting a GPR49 protein or a gene encoding a GPR49protein. Upregulation of GPR49 expression was confirmed significantly invarious cancer tissues or cancer cell lines, whereas GPR49 expression innormal cells is very low in organs other than the brain. Therefore,GPR49 is useful as a specific marker for detecting cancer.

In an embodiment of the methods of the present invention, cancer isdiagnosed by detecting a GPR49 protein in a sample. Preferably, anextracellular region of a GPR49 protein is detected. Detection of aGPR49 protein is preferably carried out using an antibody thatrecognizes a GPR49 protein.

A specific example of the methods of diagnosis of the present inventionis a method of cancer diagnosis comprising the steps of:

(a) providing a sample collected from a subject; and(b) detecting a GPR49 protein contained in the collected sample using anantibody that binds to the GPR49 protein.

In the present invention, detection includes quantitative andqualitative detection. Examples of the qualitative detection include thefollowing:

simple detection of the presence or absence of the GPR49 protein;determination of whether or not the GPR49 protein is present above acertain amount; and comparison of the amount of the GPR49 protein withthat of other samples (for example, a control sample).

On the other hand, examples of quantitative detection includemeasurement of the GPR49 protein concentration and measurement of theamount of the GPR49 protein.

Test samples of the present invention are not particularly limited aslong as they are samples that may contain a GPR49 protein. Specifically,samples collected from the body of an organism such as mammal arepreferred. Samples collected from humans are more preferred. Specificexamples of the test samples include blood, interstitial fluid, plasma,extravascular fluid, cerebrospinal fluid, synovial fluid, pleural fluid,serum, lymphatic fluid, saliva, urine, tissue, ascites, andintraperitoneal lavage. Preferred samples are those obtained from testsamples such as immobilized specimens of tissue or cells collected fromthe body of an organism, or cell culture solution.

GPR49 protein is cleaved and divided into an N-terminal peptide ofapproximately 60 kDa and a C-terminal peptide of approximately 40 kDa,and the N-terminal peptide is secreted into blood. Therefore, in thediagnostic method of the present invention, the cleaved N-terminalpeptide or the C-terminal peptide may be detected. For example, thesecreted N-terminal peptide included in a sample such as blood or serummay be detected.

The cancers that are diagnosed by the present invention are notparticularly limited and may be any cancer. Specific examples includehepatocellular carcinoma, lung cancer, prostate cancer, ovarian cancer,Ewing's sarcoma, and glioma cells (for example, glioblastoma). In thepresent invention, both primary lesions and metastatic foci of thesecancers can be diagnosed. Primary gastric cancer and metastatic gastriccancer are particularly preferable in the present invention.

In the present invention, when the protein is detected in a test sample,subject is diagnosed as having cancer using the protein level as anindicator. More specifically, if the amount of the GPR49 proteindetected in a test sample is higher than that in a negative control or ahealthy subject, it is determined that the subject has cancer or islikely to get cancer in the future. That is, the present inventionrelates to methods for diagnosing cancer which comprise the steps of:

(1) detecting a GPR49 expression level in a biological sample collectedfrom a subject; and(2) indicating that the subject has cancer if the GPR49 expression leveldetected in step (1) is higher than that of a control.

In the present invention, “control” refers to samples serving as astandard for comparison, and include negative controls and biologicalsamples from healthy subjects. Negative control can be obtained bycollecting biological samples from healthy subjects and mixing them asnecessary. The GPR49 expression level in a control can be detected inparallel with the GPR49 expression level in the biological sample of asubject. Alternatively, by detecting the GPR49 expression level inbiological samples of many healthy subjects in advance, a standardexpression level in healthy subjects can be determined statistically.Specifically, for example, the mean value±2× standard deviation (S. D.),or mean value±3× standard deviation (S. D.) may be used as the standardvalue. Statistically, 80% of the healthy subjects are within ±2×standard deviation (S. D.) from the mean value, and 90% of the healthysubjects are within ±3× standard deviation (S. D.) from the mean value.

Alternatively, the GPR49 expression level in control can be determinedusing a receiver operating characteristic (ROC) curve. An ROC curve is agraph showing detection sensitivity on the vertical axis, and falsepositive rate (i.e., “1-specificity”) on the horizontal axis. In thepresent invention, an ROC curve can be obtained by plotting the changesof sensitivity to false positive rate by continuously varying thestandard values for determining the GPR49 expression level in abiological sample.

The “standard value” for obtaining an ROC curve is a numerical valuetemporarily used for statistical analysis. In general, “standard values”for obtaining an ROC curve are continuously varied within a range thatcovers all selectable standard values. For example, the standard valuescan be varied between the minimum and maximum values of GPR49 measuredin the population analyzed.

Based on the ROC curve obtained, standard values that are expected toyield a desired detection sensitivity and accuracy can be selected.Standard values that are statistically determined by an ROC curve orsuch are also called “cut-off values”. In methods for detecting cancerbased on cut-off values, the GPR49 expression level detected in step (1)is compared to the cut-off value in step (2) described above. Then,cancer is detected in a subject if the GPR49 expression level in step(1) is higher than the cut-off value.

In the present invention, the GPR49 expression level can be determinedby any method. More specifically, the GPR49 expression level can bedetermined by evaluating the amount of GPR49 mRNA, the amount of GPR49protein, and the biological activity of GPR49 protein. The amount ofGPR49 mRNA and GPR49 protein can be determined by the methods describedherein.

Subjects in the present invention may be any animal species that expressa GPR49 protein. For example, many non-human mammals such as chimpanzees(Pan troglodytes) (ENSPTRG00000005223 (XR_(—)021586.1)), rhesus monkeys(Macaca mulatta) (ENSMMUG00000020942), mice (Mus musculus)(ENSMUSG00000020140), rats (Rattus norvegicus) (ENSRNOG00000004221(LOC687868)), guinea pigs (Cavia porcellus) (ENSCPOG00000009492), dogs(Canis familiaris) (ENSCAFG00000000451), cats (Felis catus)(ENSFCAG00000008064), and chickens (Gallus gallus) (ENSGALG00000010163)are known to express the GPR49 protein. Therefore, these animals areincluded in the subjects of the present invention. Particularlypreferred subjects are humans. As a matter of course, it goes withoutsaying that when a non-human animal is used as a subject, the GPR49protein for the animal species is detected.

Methods for detecting the GPR49 protein contained in a test sample arenot particularly limited. An immunological method using an anti-GPR49antibody for detection such as the following is preferred:

radioimmunoassay (RIA);enzyme immunoassay (EIA);fluorescence immunoassay (FIA);luminescence immunoassay (LIA);immunoprecipitation (IP);turbidimetric immunoassay (TIA);Western blotting (WB);immunohistochemical (IHC) method; andsingle radial immunodiffusion (SRID).

Of the above techniques, immunohistochemical (IHC) method is a preferredimmunological assay for methods for diagnosing cancer that comprise thestep of detecting a GPR49 protein on a section of immobilized tissue orcells obtained from a patient affected with cancer. The above-mentionedimmunological methods such as immunohistochemical (IBC) method aremethods known to those skilled in the art.

That is, GPR49 is a membrane protein whose expression is specificallyelevated in cancer cells. Therefore, cancer cells or cancer tissues canbe detected by anti-GPR49 antibodies. Cancer cells contained in cells ortissues collected from a living body are detected by the above-mentionedimmunohistochemical analysis.

In another preferred embodiment, cancer tissues in a living body can bedetected with anti-GPR49 antibodies. More specifically, the presentinvention relates to methods for detecting cancer which comprise thesteps of: (1) administering to a subject a GPR49 protein-bindingantibody labeled with a labeling substance such as radioisotopes; and(2) detecting accumulation of the labeling substance. In order to tracethe antibody administered into a living body, the antibody may belabeled to enable detection. For example, the behavior of antibodieslabeled with a fluorescent substance, luminescent substance, orradioisotope can be traced in vivo. Antibodies labeled with afluorescent substance or a luminescent substance can be observed usingan endoscope or a laparoscope. When using a radioisotope, thelocalization of an antibody can be imaged by tracing the radioactivityof the radioisotope. In the present invention, the localization ofanti-GPR49 antibodies in vivo demonstrates the presence of cancer cells.

A positron-emitting radionuclide can be used as a radioisotope forantibody labeling for detecting cancer in vivo. For example, antibodiescan be labeled with positron-emitting radionuclides such as ¹⁸F, ⁵⁵Co,⁶⁴Cu, ⁶⁶Ga, ⁶⁸Ga, ⁷⁶Br, ⁸⁹Zr, and ¹²⁴I. Anti-GPR49 antibodies can belabeled with these positron-emitting radionuclides by using knownmethods (Acta Oncol. 32, 825-830, 1993).

After administering anti-GPR49 antibodies labeled with apositron-emitting radionuclide to humans or animals, radiation emittedby the radionuclides is measured from outside the body using positronemission tomography scanner (PET), and then converted into an image bycomputed tomography methods. PET is an instrument for non-invasivelyobtaining data relating in vivo behavior of drugs and such. Radiationintensity can be quantitatively converted into an image as signalintensity using PET. By using PET as described above, antigenicmolecules that are highly expressed in a particular cancer can bedetected without collecting samples from patients. In addition to theabove-mentioned nuclides, anti-GPR49 antibodies can be radiolabeled withshort-lived nuclides using positron-emitting radionuclides such as ¹¹C,¹³N, ¹⁵O, ¹⁸F, and ⁴⁵Ti.

Production of short-lived nuclides with the above-mentioned nuclidesusing medical cyclotron, techniques for producing short-livedradiolabeled compounds, and such, are currently under research anddevelopment. Anti-GPR49 antibodies can be labeled with variousradioisotopes using such techniques. Anti-GPR49 antibodies administeredto patients accumulate at primary lesions and metastatic foci accordingto the specificity of the anti-GPR49 antibodies at each site of thepathological tissue. If the anti-GPR49 antibodies are labeled withpositron-emitting radionuclides, the presence of primary lesions andmetastatic foci can be detected from the localization of theirradioactivity by detecting the radioactivity. For use in such diagnosticpurpose, emission activity values of 25 to 4,000 keV gamma particles orpositrons can be suitably used. Furthermore, therapeutic effects can beexpected by selecting a suitable nuclide and giving in high dose. Toobtain anticancer effect by radiation, nuclides that provide emissionvalues of 70 to 700 keV gamma particles or positrons can be used.

In another embodiment of the methods of the present invention, theexpression of GPR49 gene is detected. The gene detected in the presentinvention is not particularly limited, but mRNA is preferred. In thepresent invention, detection includes quantitative and qualitativedetection. Examples of qualitative detection include the followingoperations:

simple detection of the presence or absence of GPR49 mRNA;determination of whether or not the GPR49 mRNA is present above acertain amount; andcomparison of the amount of GPR49 mRNA to that of other samples (forexample, a control sample).

On the other hand, quantitative detection includes, for example,measurement of the GPR49 mRNA concentration, and measurement of theamount of GPR49 mRNAs.

Any sample that may contain GPR49 mRNAs may be used as a test sample ofthe present invention. Samples collected from the body of an organismsuch as mammals are preferred, and samples collected from humans aremore preferred. Specific examples of the test samples include blood,interstitial fluid, plasma, extravascular fluid, cerebrospinal fluid,synovial fluid, pleural fluid, serum, lymphatic fluid, saliva, urine,tissue, ascites, and intraperitoneal lavage. Preferred samples are thoseobtained from test samples such as immobilized specimens of tissue orcells collected from the body of an organism and cell culture solution,and they are included in the test samples of the present invention.

When samples are obtained from test samples such as cell culturesolutions or specimens of immobilized tissues or cells collected fromthe body of all organism, in situ hybridization method is preferablyused. In situ hybridization method has been developed as a method forexamining the presence/absence and distribution of a specific DNA or RNAin cells or tissues and the intensity of their expression. The principlebehind this method is that the method utilizes the nature of a nucleicacid probe having a nucleotide sequence complementary to a specificnucleotide sequence in cells to specifically form a complex. When suchprobes are labeled with radioisotopes (RIs), antigenic substances(haptens), or such in advance, hybridization spot becomes discriminablethrough detection of these labels; therefore, in situ hybridizationmethod is used for detection and such of DNA, RNA, or the like in cells.RIs have been favorably used for labeling probes. More favorableexamples include use of fluorescent labeling utilizing non-radioactivesubstances, for example, haptens such as biotin or digoxigenin.Particularly favorable examples include use of detection methodsutilizing fluorescence in situ hybridization called FISH.

The cancer to be diagnosed is not particularly limited. Specificexamples include gastric cancer, colon cancer, hepatocellular carcinoma,lung cancer, prostate cancer, ovarian cancer, and glioma (for exampleglioblastoma). In the present invention, both primary lesions andmetastatic foci of these cancers can be diagnosed.

Subjects in the present invention may be any animal species thatexpresses the GPR49 protein. For example, many non-human mammals such asmice, rats, rhesus monkeys, and chimpanzees are known to express GPR49.Particularly suitable subjects are humans. When a non-human animalspecies is used as a subject, the GPR49 mRNA of the animal species isdetected.

Specific embodiments of the detection method are described below. First,a sample is prepared from a subject. Next, GPR49 mRNAs included in thesample are detected. In the present invention, cDNAs synthesized frommRNAs can also be detected. In the present invention, when GPR49 mRNAsor cDNAs encoding GPR49 is detected in a test sample, it is determinedthat the subjects are likely to have cancer. For example, if a higheramount of GPR49 mRNAs or cDNAs encoding GPR49 is detected in the testsample than in a negative control or healthy subjects, it is determinedthat the subject has cancer or is likely to become affected by cancer inthe future.

Methods for detecting mRNA are known. Specifically, for example,Northern blotting method, RT-PCR method, DNA array method, and such maybe used in the present invention.

The detection methods of the present invention described above can beautomated using various automatic testing devices. Through automation,large quantities of samples can be examined in a short period of time.

The present invention also provides diagnostic agents or kits fordiagnosing cancer which comprise reagents for detecting the GPR49protein in a test sample. The diagnostic agents of the present inventioncomprise at least an anti-GPR49 antibody.

Kits for diagnosing cancer can be produced by combining the agents fordiagnosing cancer of the present invention with another element used fordetecting GPR49. More specifically, the present invention relates tokits for diagnosing cancer which comprise an antibody that binds toGPR49 and a reagent for detecting binding between the antibody andGPR49, and further may comprise a control sample comprising a biologicalsample containing GPR49. In addition, instructions that describe themeasurement operation can be attached to the kits of the presentinvention.

All prior art references cited herein are incorporated by reference intothis description.

EXAMPLES

Herein below, the present invention will be specifically described withreference to the Examples, but it is not to be construed as beinglimited thereto.

Example 1 Analysis of the Human GPR49 mRNA Expression Using Human Exon1.0 ST Array

To elucidate the expression distribution of human GPR49 mRNA in clinicalcancer, cancer cell lines, and various normal organs, expressionanalysis was carried out using Human Exon 1.0 ST Array (Affymetrix)which was originally developed for analyzing splice variants. Theadvantage of performing expression analysis using Human Exon 1.0 STArray is that in contrast to the former expression array of Affymetrixwhich basically only had one probe set on the 3′ side for each gene,Human Exon 1.0 ST Array has at least one probe set installed for everygene exon, and therefore, when a gene-by-gene expression analysis isperformed using this array, expression data of multiple probe sets canbe obtained for each gene, and the reliability of the expression datafor every gene will increase.

In this expression analysis, the total RNAs used were derived from thetumor sites of 22 isolated lung adenocarcinoma tissues, 13 isolatedgastric cancer tissues, five Ewing's sarcoma tissues, and 20 isolatedovarian cancer tissues, 19 types of lung adenocarcinoma cell lines, fourtypes of small cell lung cancer cell lines, 16 types of gastric cancercell lines, 20 types of ovarian cancer cell lines, and 71 types ofnormal tissues (purchased from Clontech, Ambion, STRATAGENE, CellAPPLICATIONS, Panomics, CHEMICON, and BioChain Institute).

Total RNA was extracted using Trizol (Invitrogen) according to themanufacturer's protocol on tumor sites and normal sites of all isolatedclinical cancer tissues (with prior informed consent), and cancer celllines (purchased from ATCC, JCRB, and RIKEN BIOSOURCE CENTER CELL BANK).

Gene expression analysis experiments were performed following theGeneChip Whole Transcript (WT) Sense Target Labeling Assay Manual(Affymetrix) using 1 m of above-mentioned total RNAs, and the Human Exon1.0 ST Array Data was digitized using the ExACT (Exon ArrayComputational Tool) software provided by Affymetrix.

There were 21 Core Probe Sets for the human GPR49 in Human Exon 1.0 STArray, and those probe set IDs are:

3422146, 3422162, 3422166, 3422167, 3422175, 3422177, 3422179, 3422180,3422181, 3422182, 3422189, 3422191, 3422194, 3422195, 3422197, 3422198,3422199, 3422200, and 3422201.

Expression data for probe set ID 3422201 for normal tissues; gastriccancer cell line and tumor sites of isolated gastric cancer tissues;tumor sites of tissues isolated from Ewing's sarcoma, small cell lungcancer, and lung adenocarcinoma; and ovarian cancer cell lines and tumorsites of isolated ovarian cancer tissues are shown in FIG. 1; FIG. 2;FIG. 3; and FIG. 4, respectively.

As will be noted from FIGS. 1 to 4, expression of the human GPR49transcript in normal tissues is limited to the diencephalon, medullaoblongata, peripheral nerve, skeletal muscle, uterus, placenta, fetalcolon, and such. On the other hand, the expression is low in the lung,kidney, liver, bone marrow, and peripheral blood which are organs inwhich drug toxicity is of concern, and therefore it is expected thatside effects may be kept low. Among cancer tissues, high expressionlevels were observed in gastric cancer, Ewing's sarcoma, small cell lungcancer, lung adenocarcinoma, and ovarian cancer, and anti-tumor agentstargeting human GPR49 are expected to be effective against these typesof cancer.

Example 2 Establishment of Cells Expressing the Full-Length Human GPR49

The full-length human GPR49 cDNA was isolated by the PCR method based onNCBI Accession Nos. NP_(—)003658.1 (SEQ ID NO: 1 (amino acid sequence))and NM_(—)003667.2 (SEQ ID NO: 2 (nucleotide sequence)) respectively,and then cloned into a mammalian cell expression vector (pcDNA5/FRT/TO)(Invitrogen). pcDNA5/FRT/TO enables inducible expression of a insertedgene under the control of a hybrid human CMV/TetO₂ promoter, and is avector into which a neomycin resistance gene has been inserted as a drugresistance marker. Additionally, using the FlpIn expression system(Invitrogen) which enables inducible expression only in the presence oftetracycline or doxycycline, the full-length human GPR49 cDNA wastransfected into 293FlpIn T-Rex cells. Fugene6 (Roche) was used fortransfecting the expression vector into the 293FlpIn T-Rex cellscultured in DMEM (high glucose)/10% FBS/100 μg/mL Zeocin™(Invitrogen)/15 μg/mL blasticidin (Invitrogen). pcDNA5/FRT/GPR49 vectortogether with the pOG44 vector that expresses Flp recombinase weretransfected following the instruction manual, and full-length humanGPR49-transfected cell lines B2 and B4 with inducible expression ofhuman GPR49 were established by 50 μg/mL hygromycin B (Invitrogen)selection. For an HA-tag was inserted at the N-terminus of the GPR49gene inserted into the expression vector, selected cells were detectedby an anti-HA antibody (Sigma).

The vector was transfected into DG44 cell line, which is derived fromChinese hamster ovary, using a BioRad Gene Pulser to obtainHA-GPR49-expressing cell line 2B10.

Furthermore, a vector introduced with the GPR49 gene was constructed forDNA immunization. The expression vector pMCN enables induction andexpression of a transferred gene under the control of a mouse CMVpromoter (ACCESSION No. U68299), and is a vector into which a neomycinresistance gene has been incorporated as a drug resistance marker. AGPR49 expression vector pMCN-GPR49 was prepared by cloning the GPR49gene into pMCN using a conventional method.

Example 3 Production of Anti-GPR49 Monoclonal Antibodies by DNAImmunization

DNA immunization by gene transfer to mice was carried out by the GeneGunParticle method. The procedure was performed according to the BioRadmanual. The bullets for DNA immunization were prepared by mixing 1 mmGold particles (BioRad) and pMCN-GPR49 DNA, and coating the interior ofa tube with them. Gene was transferred by shooting the bullets coatedwith pMCN-GPR49 DNA into the abdominal skin of a 6-week-old femaleMRL/lpr mouse using a Helios Gene Gun (BioRad) at a pressure of 200 to300 psi. The gene transferred to the keratinocytes, Langerhans cells,and dermal dendritic cells in the skin is thought to evoke immunitybecause these cells become antigen-presenting cells (APC) by expressingthe GPR49 protein (Methods 31, 232-242 (2003); Immunization with DNAthrough the skin). DNA immunization was carried out six times at oneweek intervals. As the final immunization, 1,000,000 GPR49-expressingDG44 cell lines 2B10 were diluted with PBS and administered into thetail vein. Measurement of the antibody titer was performed by FACSanalysis using 2B10 cells. A comparison was made of the reactivity ofsera from the immunized mice to GPR49 protein expressed on surfacemembranes of 2B10 cells. Mouse showing the highest response wassubjected to final immunization and then cell fusion. The spleen cellswere resected three days after the final immunization and mixed withP3-X63Ag8U1 mouse myeloma cells (P3U1, purchased from ATCC) at a 2:1ratio. Cell fusion was carried out by gradually adding PEG1500 (RocheDiagnostics), and hybridomas were prepared. After the PEG 1500concentration was diluted by carefully adding RPMI 1640 medium (GibcoBRL), the PEG1500 was removed by a centrifugation procedure. Then, thehybridomas were suspended in RPMI 1640 medium containing 10% FBS, 1×HATmedia supplement (SIGMA), and 0.5×BM-Condimed H1 Hybridoma cloningsupplement (Roche Diagnostics) (hereinafter, HAT medium), and seededinto a 96-well culture plate to a total volume of 200 μL/well. The celldensity at the time of seeding was diluted depending on the number ofP3U1 cells used, and the hybridomas were cultured for about one week inHAT medium in the 96-well culture plate at 37° C. and 5% CO₂. Screeningfor hybridomas that secreted antibodies into the culture supernatant wasperformed by flow cytometry.

Example 4 Preparation of sGPR49Fc

The fragment comprising the amino acids of positions 1-555 in the GPR49protein was amplified by PCR, and a vector was constructed such that itwill be expressed as a fusion protein with Fe protein of mouse IgG2a.The vector was transfected into DG44 cells, and a cell that can expressthe sGPR49Fc fusion protein was selected as the neomycin-resistant cellline. The obtained cell line, 2D3, was mass cultured, the culturesupernatant was collected, and the sGPR49Fc protein was purified. ThesGPR49Fc protein affinity-purified as an Fc fusion protein using aProtein A column served as an antigen for protein immunization or anantigen for screening hybridomas.

Example 5 Preparation of Anti-GPR49 Antibody by sGPR49Fc ProteinImmunization

50 μg of the affinity-purified sGPR49Fc protein was mixed with Freund'scomplete adjuvant for immunization, and 50 μg of the affinity-purifiedsGPR49Fc protein mixed with Freund's incomplete adjuvant was used forsubcutaneous immunization of mice twice to induce antibodies. To themouse showing the highest reactivity to the GPR49 protein, 25 μg of thesGPR49Fc protein was injected into the tail vein, cell fusion wasconducted three days later, and then hybridomas were prepared asdescribed above.

Example 6 Evaluation of Binding Activity by Flow Cytometry (FACS)

The binding to the human GPR49/DG44 cells (2B10) was evaluated by flowcytometry using the obtained hybridomas. The cell lines expressing humanGPR49 suspended in FACS buffer (2% FBS/PBS/0.05% NaN₃) were diluted to1×10⁶ cells/mL with FACS buffer, and then aliquoted at 50 μL/well into aFalcon 353910 round-bottom 96-well plate. Hybridoma culture supernatantdiluted to a suitable concentration was added to the wells containingthe cells and reacted for 60 minutes on ice. Then, the cells were washedonce with FACS buffer. Goat F(ab′)₂ fragment anti-mouse IgG(H+L)-FITC(Beckman Coulter) was added to the wells containing the cells as asecondary antibody, and reacted for 30 minutes on ice. After reaction,the supernatant was removed by centrifugation, and then the cellssuspended in 100 μL of FACS buffer were subjected to flow cytometry. AFACS Calibur (Becton Dickinson) was used for flow cytometry. The viablecell population was gated with a forward scatter-side scatter dot blot,an FL1 histogram was made of the cells contained in the population, andbinding activity thereof was evaluated.

When the hybridoma supernatants were reacted with 2B10 in which GPR49 isinduced and expressed in DG44 cells and with the parental cell line DG44respectively, hybridomas that specifically reacted with GPR49-expressingcells were obtained. The hybridomas from these wells were made intosingle clones by the limiting dilution method. The isotype of eachantibody was analyzed using an IsoStrip™ mouse monoclonal antibodyisotyping kit (Roche Diagnostics). As a result, 2J18-1N and 2J18-3 wereIgM, and 2L7-8, 2L9-3, 2L10-19, 2L13-3, 2L15-12, 2L16-15, 2L18-15,2L33-6, 2L34-5, 2L36-12, 2T4E-6, 2T9E1#14, 2T15E-2, 2T42E-4, 2T54-2,2T65-3, 2T37-16, 2U1E-1, 2U2E-2, and 2U4E-11 were IgG1. Culturing of thehybridomas made into single clones was scaled up, and then theantibodies were purified from the culture supernatant using a protein Gcolumn in accordance with the manual. The IgM antibodies were purifiedusing a protein L column in accordance with the manual. The purifiedantibodies were quantified by DC Protein Assay or such.

Example 7 Cloning of Antigen Genes

The antibody variable region gene sequences of the six hybridomas,2J18-1N, 2U1E-1, 2U2E-2, 2L13-3, 2L36-12, and 2T15E-2 that showed ADCCactivity and CDC activity were determined. The antibody genes wereamplified by RT-PCR method using total RNAs extracted from therespective hybridomas producing the anti-GPR49 antibodies, 2J18-1N,2U1E-1, 2U2E-2, 2L13-3, 2L36-12, and 2T15E-2. Hereinafter, the genenames for the respective antibodies, 2J18-1N, 2U1E-1, 2U2E-2, 2L13-3,2L36-12, and 2T15E-2, will be abbreviated as 2J18, 2U1E, 2U2E, 2L13,2L36, and 2T15E genes. The total RNA was extracted from 1×10⁷ hybridomasusing RNeasy Plant Mini Kits (QIAGEN). A RACE library was constructedfrom 1 μg of total RNA using a SMART RACE cDNA Amplification Kit(CLONTECH). 5′ end gene fragments of the gene encoding the antibodyproduced in the hybridoma were amplified using a syntheticoligonucleotide MHC-IgM (SEQ ID NO: 61; CCACCAGATTCTTATCAGACAGG) whichis complementary to the murine IgM constant region sequence for IgMantibody 2J18-1N, using the synthetic oligonucleotide MHC-IgG1 (SEQ IDNO: 62; GGGCCAGTGGATAGACAGATG) which is complementary to the murine IgG1constant region sequence for other antibody genes, or using thesynthetic oligonucleotide kappa (SEQ ID NO: 63; GCTCACTGGATGGTGGGAAGATG)which is complementary to the murine K-chain constant region nucleotidesequence. Reverse transcription reaction was carried out at 42° C. for1.5 hours. 50 μL of a PCR solution contained 5 μL of 10× Advantage 2 PCRBuffer, 5 μL of 10× Universal Primer A Mix, 0.2 mM dNTPs (dATP, dGTP,dCTP, dTTP), 1 μL of Advantage 2 Polymerase Mix (all manufactured byCLONTECH), 2.5 μL of reverse transcription reaction product, and 10 pmolof the synthetic oligonucleotide MHC-IgM, MHC-IgG1, or kappa. The PCRreaction was carried out as follows: reaction at initial temperature of94° C. for 30 seconds, 5 cycles with 5 seconds at 94° C., and 3 minutesat 72° C.; next 5 cycles with 5 seconds at 94° C., 10 seconds at 70° C.,and 3 minutes at 72° C.; and then 25 cycles with 5 seconds at 94° C., 10seconds at 68° C., and 3 minutes at 72° C. Finally, the reaction productwas heated for 7 minutes at 72° C. Each PCR product was purified fromagarose gel using a QIAquick Gel Extraction Kit (QIAGEN). Then the PCRproduct was cloned into a pGEM-T Easy vector (manufactured by Promega)and the nucleotide sequence was determined.

For 2J18, SEQ ID NO: 3 shows the nucleotide sequence and SEQ ID NO: 4shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 8 shows the nucleotide sequence and SEQ ID NO: 9 shows the aminoacid sequence of the L chain variable region. In addition, for 2J18, SEQID NO: 5 shows the amino acid sequence of heavy chain CDR1, SEQ ID NO: 6shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 7 showsthe amino acid sequence of heavy chain CDR3, SEQ ID NO: 10 shows theamino acid sequence of light chain CDR1, SEQ ID NO: 11 shows the aminoacid sequence of light chain CDR2, and SEQ ID NO: 12 shows the aminoacid sequence of light chain CDR3.

For 2U1E, SEQ ID NO: 13 shows the nucleotide sequence and SEQ ID NO: 14shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 18 shows the nucleotide sequence and SEQ ID NO: 19 shows the aminoacid sequence of the L chain variable region. In addition, for 2U1E, SEQID NO: 15 shows the amino acid sequence of heavy chain CDR1, SEQ ID NO:16 shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 17shows the amino acid sequence of heavy chain CDR3, SEQ ID NO: 20 showsthe amino acid sequence of light chain CDR1, SEQ ID NO: 21 shows theamino acid sequence of light chain CDR2, and SEQ ID NO: 22 shows theamino acid sequence of light chain CDR3.

For 2U2E, SEQ ID NO: 23 shows the nucleotide sequence and SEQ ID NO: 24shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 28 shows the nucleotide sequence and SEQ ID NO: 29 shows the aminoacid sequence of the L chain variable region. In addition, for 2U2E, SEQID NO: 25 shows the amino acid sequence of heavy chain CDR1, SEQ ID NO:26 shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 27shows the amino acid sequence of heavy chain CDR3, SEQ ID NO: 30 showsthe amino acid sequence of light chain CDR1, SEQ ID NO: 31 shows theamino acid sequence of light chain CDR2, and SEQ ID NO: 32 shows theamino acid sequence of light chain CDR3.

For 2L13, SEQ ID NO: 33 shows the nucleotide sequence and SEQ ID NO: 34shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 38 shows the nucleotide sequence and SEQ ID NO: 39 shows the aminoacid sequence of the L chain variable region. In addition, for 2L13, SEQID NO: 35 shows the amino acid sequence of heavy chain CDR1, SEQ ID NO:36 shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 37shows the amino acid sequence of heavy chain CDR3, SEQ ID NO: 40 showsthe amino acid sequence of light chain CDR1, SEQ ID NO: 41 shows theamino acid sequence of light chain CDR2, and SEQ ID NO: 42 shows theamino acid sequence of light chain CDR3.

For 2L36, SEQ ID NO: 43 shows the nucleotide sequence and SEQ ID NO: 44shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 48 shows the nucleotide sequence and SEQ ID NO: 49 shows the aminoacid sequence of the L chain variable region. In addition, for 2L36, SEQID NO: 45 shows the amino acid sequence of heavy chain CDR1, SEQ ID NO:46 shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 47shows the amino acid sequence of heavy chain CDR3, SEQ ID NO: 50 showsthe amino acid sequence of light chain CDR1, SEQ ID NO: 51 shows theamino acid sequence of light chain CDR2, and SEQ ID NO: 52 shows theamino acid sequence of light chain CDR3.

For 2T15E, SEQ ID NO: 64 shows the nucleotide sequence and SEQ ID NO: 65shows the amino acid sequence of the H chain variable region; and SEQ IDNO: 69 shows the nucleotide sequence and SEQ ID NO: 70 shows the aminoacid sequence of the L chain variable region. In addition, for 2T15E,SEQ ID NO: 66 shows the amino acid sequence of heavy chain CDR1, SEQ IDNO: 67 shows the amino acid sequence of heavy chain CDR2, SEQ ID NO: 68shows the amino acid sequence of heavy chain CDR3, SEQ ID NO: 71 showsthe amino acid sequence of light chain CDR1, SEQ ID NO: 72 shows theamino acid sequence of light chain CDR2, and SEQ ID NO: 73 shows theamino acid sequence of light chain CDR3.

Example 8 Western Blotting Using the Cell Lysates from Cell Line withForced Expression

Antibodies that can be used for Western blotting were screened using thecell lysate of 2B10 expressing HA-GPR49 in DG 44 cell line, 2U1E-1,2U2E-2, 2U4E-11, 2T15E-2, 2T65-3, and such were able to detect a band of100-kDa molecular weight predicted as the GPR49 protein by Westernblotting. To confirm that the detected 100-kDa band is derived fromhuman GPR49, the reactivities with the cell lysates obtained fromnon-induced and induced HA-GPR49-expressing 293 cells B2, in whichHA-GPR49 expression can be induced with doxocycline, were analyzed byWestern blotting. The results are shown in FIG. 5. In 293 and B2, 0refers to cell lysates without induction, and 1 and 10 refer to celllysates with induction. Using monoclonal antibody 2U2E-2, 100-kDa bandswere confirmed to be detectable specific to the inducibly expressedlanes. Since the size of this band was the same as the 100-kDa band forthe HA-GPR49 band detected by the HA-tag, it was concluded thatmonoclonal antibody 2U2E-2 is an antibody that recognizes GPR49.

Example 9 Confirmation of Antibody-Recognized Antigen Using siRNA

To further confirm that the 100-kDa band is a GPR49-derived band, GPR49expression was knocked down by transfecting siRNAs, and disappearance ofa band recognized by the antibody was confirmed. siRNAs against GPR49(Cat. No. 1299003) LGR5-HSS112507, LGR5-HSS112508, LGR5-HSS112509(hereinafter abbreviated as siRNA 507, 508, and 509) purchased fromInvitrogen were transfected into the 2B10 cell line or colon cancer cellline LoVo cells which highly express GPR49 according to the manual, andtheir cell lysates were analyzed by Western blotting. As a result, asshown in FIG. 6, a band corresponding to a 100-kDa protein having themolecular weight predicted for GPR49 was markedly eliminated for siRNAs508 and 509 among the three siRNAs 507, 508, and 509 used, the 100-kDaband was considered to indicate recognition of GPR49.

Furthermore, as shown in FIG. 6, as a result of Western blotting using2U1E-1 and 202E-2, a new band that is eliminated along with the 100-kDaprotein band eliminated as a result of siRNA introduction wasidentified. In the detection using the 2U1E-1 antibody, an approximately40-kDa protein band was eliminated in addition to the 100-kDa proteinband due to siRNA. In the detection using the 2U2E-2 antibody, anapproximately 60-kDa protein band was found to be eliminated in additionto the 100-kDa protein band due to siRNA. Since the total size of thesetwo bands exactly yields 100 kDa corresponding to the full length, GPR49protein may be cleaved somewhere to yield 60-kDa and 40-kDa proteins.The 60-kDa and 40-kDa bands were also detected in colon cancer cell lineLoVo cells.

Example 10 Detection of the Cleaved Fragments by Immunoprecipitation

To confirm the presence of the 40-kDa and 60-kDa protein bands detectedin Western blotting, immunoprecipitation experiments were carried outusing GPR49 monoclonal antibodies. Cell lysate prepared by solubilizingHA-GPR49-expressing DG44 cell line 2B10 in NP40 lysis buffer (0.5% NP40,50 mM Tris-HCl (pH7.5), 150 mM NaCl, protease inhibitor complete mini(Roche)) was used as the sample for immunoprecipitation. The amount ofprotein included in the cell lysate was quantified by DC Protein Assayusing BSA as a standard. A solution containing 2 μg of antibody wasadded to 500 μL of cell lysate containing 100 μg of protein, and thiswas reacted at 4° C. for one hour. Additionally, 20 μL of Protein A/GPlus agarose (Santa Cruz) was added and this was reacted overnight.Agarose beads were centrifugated at 1,000×g for one minute, washed twicewith 1 mL of PBS, and then antigens bound to the antibodies were elutedby adding 50 μL of 2×SDS-sample buffer and warming at 60° C. for 30minutes. After centrifuging at 1,000×g for one minutes, 15 μL, of thesupernatant obtained was subjected to SDS-PAGE. Samples were transferredto Immobilon-P (Millipore) by a submarine method, monoclonal antibodies2U1E-1 and 2U2E-2 were used for detection. These results are shown inFIGS. 7 and 8. As is seen in the lanes for the samplesimmunoprecipitated using 2L13-3 and 2L36-12, a 40-kDa band and a 60-kDaband in addition to the 100-kDa band could surely be detected using2U1E-1 and 2U2E-2, respectively. This showed that GPR49 exists asmolecules having molecular weights indicated by sizes of approximately60 kDa and 40 kDa in addition to 100 kDa. HRP-labeled anti-mouseIgG(H+L) antibody (manufactured by Jackson ImmunoResearch Laboratories)was used as the secondary antibody in FIG. 7, and HRP-labeled anti-mousekappa antibody (manufactured by Southern Biotech) was used as thesecondary antibody for distinguishing the band derived from the H chainof the antibody used for immunoprecipitation from the 60-kDa GPR49 bandin FIG. 8.

Example 11 Western Blotting Using the Cell Lysates of Various CancerCell Lines

Cell lysates from various cancer cell lines were subjected to detectionusing monoclonal antibody 2U2E-2. As shown in FIG. 9, GPR49 proteinexpression is remarkably upregulated particularly in colon cancer cellline LoVo, hepatocellular carcinoma cell lines Alexander and HepG2,ovarian cancer cell lines KURAMOCHI and OVSAHO, and glioma U251. Thearrows indicate the 100-kDa and 60-kDa protein bands. The lanes in thephotograph have their sample names indicated and are colon cancer cellline LoVo, gastric cancer cell line NUGC-4, hepatocellular carcinomacell line Alexander, hepatocellular carcinoma cell line HepG2,hepatocellular carcinoma cell line Huh6, ovarian cancer cell lineKURAMOCHI, ovarian cancer cell line OVSAHO, glioma U251, Chinese hamsterovary cell DG44, and HA-GPR49-expressing D044 cell line 2B10,respectively.

Example 12 Measurement of CDC Activity of the Anti-GPR49 MonoclonalAntibodies

CDC activity was measured using the degree of 7-AAD uptake into damagedcells as an indicator.

GPR49-expressing DG44 cells or DG44 cells were reacted at 4° C. for 30minutes with a 10 μg/mL of monoclonal antibody. Next, Baby RabbitComplement (CEDARLANE LABORATORIES) was added at a final concentrationof 1% or 5%, and the reaction was continued at 37° C. for 90 minutes.After addition of 7-AAD (Beckman Coulter) at a final concentration of 1μg/mL, this was left to stand at room temperature for ten minutes.Thereafter, the cells were washed with FACS buffer, and then the ratioof damaged cells was analyzed with a FACS Calibur. The value of % FL3indicates the proportion of damaged cells stained with 7-AAD, andcomplement-dependent cytotoxicity (CDC) activity in HA-GPR49-expressingDG44 cells was observed specifically when using anti-GPR49 antibody2J18-1N (FIG. 10).

Example 13 Construction of the 2J18 scFv-Fc Expression Vector

Since anti-human GPR49 monoclonal antibody 2J18 is an IgM, ADCC activitycannot be evaluated. Therefore the antibody gene was expressed as a formof scFv-Fc. As described in Example 7, H chain and L chain variableregions of the cloned 2J18 antibody gene were amplified by PCR, theywere linked by a GGGGS amino acid as a linker, and then an antibodymolecule expressed as the form of scFv-Fc was produced by ligating thehinge region, CH2 region, and CH3 region of the mouse IgG2a H chain.Specifically, PCR was carried out using the following primers:

KozakATG-2J18VH (SEQ ID NO: 74) GCGAATTCCACCATGGGATG; 2J18VH-GS1(SEQ TD NO: 75) TGAGCCACCGCCACCTGCAGAGACAGTGACCAGAG; GSI-2J18VL(SEQ ID NO: 76) GGTGGCGGTGGCTCACAGATTGTTCTCACCCAGTC; 2J18VH-GS2(SEQ ID NO: 77) ACTCCCACCACCGCCTTTTATTTCCAATTTTGTCCCCG; GS2-mIgG2a-hinge(SEQ ID NO: 78) GGCGGTGGTGGGAGTGAGCCCAGAGGGCCCAC; and NX-mG2a-3(SEQ ID NO: 79) CTCTAGAGCGGCCGCTTATC.

These were inserted into an expression vector to complete the2J18scFv-Fc expression vector.

Example 14 Preparation of the 2J18 scFv-Fc Protein

The 2J18scFv-Fc expression vector was transiently expressed in 293Tcells, and the protein was affinity purified from the culturesupernatant using a Protein G column. 18 μg of plasmid DNA was mixedwith 54 μL of Fugene HD (manufactured by Roche) in 900 μL of Opti-MEM(manufactured by Invitrogen), this was left to stand for 15 minutes, andthen the mixture was poured onto 2,000,000 293T cells (purchased fromATCC) cultured in a T75 flask to transfer the gene into the cells. Afterculturing in a 5% CO₂ incubator at 37° C. for three days, the culturesupernatant was collected, and 2J18scFV-Fc was purified using a ProteinG column according to the manual.

Example 15 Preparation of the Human IgG1 Chimeric Antibody 2L13

The H chain and L chain variable regions of the antibody gene ofanti-human GPR49 monoclonal antibody 2L13 cloned as in Example 7 wereamplified by PCR, they were ligated with the H chain and L chainconstant regions of human IgG1, and inserted into an expression vectorso that they can be expressed as a human IgG1 chimeric molecule. Theobtained vector was transfected into rat myeloma cell YB2/0 (purchasedfrom ATCC) to establish a neomycin-resistant line. The cells werecultured in RPMI-1640/10% FBS/500 μg/mLGeneticin/penicillin-streptomycin, and human IgG 1 chimeric antibody waspurified from the culture supernatant using a Protein A column accordingto the manual. The purified antibody 2L13/YB was subjected to ADCCactivity measurements.

Example 16 Measurement of ADCC Activity of the Anti-GPR49 MonoclonalAntibodies

The ADCC activity of an anti-human GPR49 monoclonal antibody against2B10, which is a DG44 cell forcedly expressing GPR49, was investigatedby the Chromium release assay. The target cell 2B10 was cultured for afew hours in Chromium-51-supplemented culture medium (CHO-S SFM H(manufactured by Invitrogen)), then the culture medium was removed, andafter washing the cells with the culture medium, the cells suspended ina fresh culture medium were added to a 96-well round-bottom plate at1×10⁴ cells per well. Subsequently, the antibody was added to finalconcentrations of 1 μg/mL and 0.1 μg/mL, an effector cell (a recombinantcell (Japanese Patent Application No. 2007-20155) produced by forcedlyexpressing a chimeric protein comprising the extracellular regions of amouse Fe-gamma receptor 3 (NM_(—)010188) and the transmembrane regionsand intracellular regions of a human gamma chain (NM_(—)004106) in NK-92(ATCC, CRL-2407)) was added to each well at approximately five-times theamount of the target cell, and the plate was left to stand in a 5% CO₂incubator at 37° C. for four hours. Then, the plate was centrifuged, afixed amount of the supernatant was collected from each well, andradioactivity was measured using a Wallac 1480 gamma counter, and thespecific chromium release rate (%) was determined using the followingequation:

Specific chromium release rate(%)=(A−C)×100/(B−C)

Here, A represents the radioactivity in each well, B represents the meanvalue of radioactivity released into the medium upon cell lysis byNonidet P-40 at a final concentration of 1%, and C represents the meanvalue of radioactivity when only medium is added.

As a result, as shown in FIG. 11, among the anti-human GPR49 monoclonalantibodies used in the examination, 2T54-2, 2T15E-2, 2L13-3, 2L36-12,and 2J18scFv-Fc in particular showed very strong ADCC activity inductionagainst human GPR49-expressing cell 2B10. The present result showed thatantibody therapy against tumors targeting human GPR49 is very useful.

The ADCC activity of human IgG 1 chimeric antibody 2L13/YB was measuredby using a 2B10 cell for the target cell as described above, adding aneffector cell (a recombinant cell (Japanese Patent Application No.2007-20155) produced by forcedly expressing human Fe-gamma receptor 3(NM_(—)000569) in NK-92 (ATCC, CRL-2407)) at approximately five-timesthe amount of the target cell, and allowing the plate to stand in a 5%CO₂ incubator at 37° C. for four hours. Then, this plate wascentrifuged, a fixed amount of the supernatant was collected from eachwell, radioactivity was measured with a Wallac 1480 gamma counter, andthe specific chromium release rate (%) was determined using theequation. As a result, as shown in FIG. 11, very high ADCC activity wasobserved against human GPR49-expressing cells with 2L13/YB.

Example 17 Cytocidal (Cell-Killing) Effect by Internalization UsingMab-Zap

As a model for development of an antibody pharmaceutical whose mode ofaction involves binding of antibody conjugated with a toxin or such tothe target cell followed by internalization into the cell, and thenkilling the target cell by the function of the conjugated toxin, Mab-Zap(manufactured by Advanced Targeting Systems) to which a toxin calledsaporin is conjugated was used as a secondary antibody to evaluate thecell killing ability against GPR49-expressing cells. The antibody andMab-Zap was added at 100 ng/well to B4 cells with induced and uninducedexpression of HA-GPR49 incubated in a 5% CO₂ incubator at 37° C. forthree days, the number of viable cells was analyzed by WST8 assay usinga viable cell count reagent SF (Nacalai Tesque). The results are shownin FIG. 12. Cytotoxic activity was confirmed in all of the antibodiesanalyzed except for 2T42E-4, 2U2E-2, and 2U4E-11.

Example 18 Expression and Epitope Analysis of GST Fusion Protein

As a result of analyzing 2U1E-1 which recognizes the 40-kDa band throughWB by constructing a deletion mutant GPR49 expression vector, an epitopewas found to exist in the amino acids from positions 495 to 537. Tonarrow the region, the amino acids from positions 495 to 537, 495 to516, 510 to 529, and 517 to 537 were fused and expressed as GST fusionproteins. The amino acid sequences of GPR49 included in each of the GSTfusion proteins are shown in FIG. 13. As a result of analysis by Westernblotting using the expression products, as shown in FIG. 14, the aminoacid region from position 517 to 537 was found to be the epitope for2U1E-1. Similarly, when an epitope of the 2T15E-2 antibody which alsorecognizes the 40-kDa fragment was analyzed, an epitope existed in theamino acid region from position 510 to 529. From these results, the40-kDa protein resulting from cleavage can be said to be a moleculecomprising the sequence at least up to amino acid position 510.

Example 19 Reactivity of an Anti-GPR49 Monoclonal Antibody with MouseGPR49

As shown in FIG. 15, when mouse GPR49 was incorporated into anexpression vector, the protein was expressed transiently in 293T cells,and then the cell lysate was analyzed by WB, the antibody was found toalso react against mouse GPR49.

Example 20 Evaluation of Binding Activity by Flow Cytometry (FACS)

The reactivity of 2T15E-2 antibody to human cancer cell lines wereanalyzed by flow cytometry. Human cancer cell lines suspended in a FACSbuffer (2% FBS/PBS/0.05% NaN₃) were diluted to 1×10⁶ cells/mL with theFACS buffer, and the solutions were then dispensed into a Falcon 353910round-bottom 96-well plate at 50 μL/well. 2T15E-2 antibody diluted to aconcentration of 10 μg/mL was added, and this was reacted for 60 minuteson ice. Next, the cells were washed once with the FACS buffer. Afteradding Goat F(ab′)₂ fragment anti-mouse IgG (Fcγ)-FITC (Beckman Coulter)as a secondary antibody to the wells containing the cells, this wasreacted for 30 minutes on ice. After the reaction, the supernatant wasremoved by centrifugation, and then the cells were suspended in 100 μLof FACS buffer containing propidium iodide (PI) and then subjected toflow cytometry. A FACS Calibur (Becton Dickinson) was used for the flowcytometry. The viable cell population was gated with a forwardscatter-side scatter dot blot, an FL1 histogram was made of the cellscontained in the population, and binding activity thereof was evaluated.

In flow cytometry analyses using ovarian cancer cell line OVSAHO,hepatocellular carcinoma cell line Alexander, and gastric cancer cellline NUGC-4, the peaks clearly shifted compared with the peaks obtainedwithout a primary antibody; therefore, this showed that the GPR49molecule exists on the cell membranes of these cell lines (FIG. 16). Thepeaks indicated with a solid line indicate the reactivity with cancercell lines, and the shaded regions represent the peaks obtained when thereactions are carried out without antibodies. The horizontal axisindicates intensity of signals according to the degree of bonding by theFITC-conjugated antibodies, and the vertical axis indicates the numberof cells.

INDUSTRIAL APPLICABILITY

Antibodies specific to the GPR49 proteins in the present invention canbe used as diagnostic agents for gastric cancer, colon cancer,hepatocellular carcinoma, lung cancer, prostate cancer, ovarian cancer,Ewing's sarcoma, glioma, and such. Diagnostic agents of the presentinvention are useful for diagnosis of primary or metastatic cancer.Specifically, detection of a GPR49 protein included in a biologicalsample collected from a patient determines possibility of cancer in thepatient. Alternatively, detection of the localization ofGPR49-expressing cells in vivo, allows detection of the presence ofgastric cancer, colon cancer, hepatocellular carcinoma, lung cancer,prostate cancer, ovarian cancer, Ewing's sarcoma, and glioma in vivo.

Furthermore, anti-GPR49 antibodies having cytotoxic activity of thepresent invention are useful for treating or preventing cancersexpressing GPR49 protein. Specifically, cytotoxic agents or cell growthinhibitors for cancer cells from various types of cancers such asgastric cancer, colon cancer, hepatocellular carcinoma, lung cancer,prostate cancer, ovarian cancer, Ewing's sarcoma, and glioma areprovided based on the present invention. The cytotoxic agents or cellgrowth inhibitors for cancer cells according to the present inventioncan be applied to both primary and metastatic cancers.

Moreover, anti-GPR49 antibodies having cytotoxic activity according tothe present invention can be used as therapeutic agents against varioustypes of cancers such as gastric cancer, colon cancer, hepatocellularcarcinoma, lung cancer, prostate cancer, ovarian cancer, Ewing'ssarcoma, and glioma. In the present invention, anti-GPR49 antibodies arealso useful as therapeutic agents against both primary and metastaticcancers.

In addition, antibody-encoding genes of the present invention, andrecombinant cells transformed by these genes can be used to producerecombinant antibodies having the above-mentioned effects or having morepreferable effects.

1. An antibody that binds to a GPR49 protein, and wherein the antibodyhas cell proliferation inhibitory activity against cells expressing theGPR49 protein.
 2. The antibody of claim 1, wherein the cellproliferation inhibitory activity is cytotoxic activity.
 3. The antibodyof claim 2, wherein the cytotoxic activity is antibody-dependentcytotoxic activity.
 4. The antibody of claim 2, wherein the cytotoxicactivity is complement-dependent cytotoxic activity.
 5. The antibody ofclaim 1, wherein a cytotoxic substance is bound to the antibody.
 6. Theantibody of claim 5, wherein the antibody has an internalizing activity.7. The antibody of claim 1, which suppresses cancer cell proliferation.8. The antibody of claim 7, wherein the cancer cell is any one ofgastric cancer cells, colon cancer cells, liver cancer cells, lungcancer cells, ovarian cancer cells, Ewing's sarcoma cells, and gliomacells.
 9. The antibody selected from any of (1) to (20) below: (1) anantibody comprising an H chain having the amino acid sequence of SEQ IDNO: 5 as CDR1, the amino acid sequence of SEQ ID NO: 6 as CDR2, and theamino acid sequence of SEQ ID NO: 7 as CDR3; (2) an antibody comprisingan L chain having the amino acid sequence of SEQ ID NO: 10 as CDR1, theamino acid sequence of SEQ ID NO: 11 as CDR2, and the amino acidsequence of SEQ ID NO: 12 as CDR3; (3) an antibody comprising the Hchain of (1) and the L chain of (2); (4) an antibody comprising an Hchain having the amino acid sequence of SEQ ID NO: 15 as CDR1, the aminoacid sequence of SEQ ID NO: 16 as CDR2, and the amino acid sequence ofSEQ ID NO: 17 as CDR3; (5) an antibody comprising an L chain having theamino acid sequence of SEQ ID NO: 20 as CDR1, the amino acid sequence ofSEQ ID NO: 21 as CDR2, and the amino acid sequence of SEQ ID NO: 22 asCDR3; (6) an antibody comprising the H chain of (4) and the L chain of(5); (7) an antibody comprising an H chain having the amino acidsequence of SEQ ID NO: 25 as CDR1, the amino acid sequence of SEQ ID NO:26 as CDR2, and the amino acid sequence of SEQ ID NO: 27 as CDR3; (8) anantibody comprising an L chain having the amino acid sequence of SEQ IDNO: 30 as CDR1, the amino acid sequence of SEQ ID NO: 31 as CDR2, andthe amino acid sequence of SEQ ID NO: 32 as CDR3; (9) an antibodycomprising the H chain of (7) and the L chain of (8); (10) an antibodycomprising an H chain having the amino acid sequence of SEQ ID NO: 35 asCDR1, the amino acid sequence of SEQ ID NO: 36 as CDR2, and the aminoacid sequence of SEQ ID NO: 37 as CDR3; (11) an antibody comprising an Lchain having the amino acid sequence of SEQ ID NO: 40 as CDR1, the aminoacid sequence of SEQ ID NO: 41 as CDR2, and the amino acid sequence ofSEQ ID NO: 42 as CDR3; (12) an antibody comprising the H chain of (10)and the L chain of (11); (13) an antibody comprising an H chain havingthe amino acid sequence of SEQ ID NO: 45 as CDR1, the amino acidsequence of SEQ ID NO: 46 as CDR2, and the amino acid sequence of SEQ IDNO: 47 as CDR3; (14) an antibody comprising an L chain having the aminoacid sequence of SEQ ID NO: 50 as CDR1, the amino acid sequence of SEQID NO: 51 as CDR2, and the amino acid sequence of SEQ ID NO: 52 as CDR3;(15) an antibody comprising the H chain of (13) and the L chain of (14);(16) an antibody comprising an H chain having the amino acid sequence ofSEQ ID NO: 66 as CDR1, the amino acid sequence of SEQ ID NO: 67 as CDR2,and the amino acid sequence of SEQ ID NO: 68 as CDR3; (17) an antibodycomprising an L chain having the amino acid sequence of SEQ ID NO: 71 asCDR1, the amino acid sequence of SEQ ID NO: 72 as CDR2, and the aminoacid sequence of SEQ ID NO: 73 as CDR3; (18) an antibody comprising theH chain of (16) and the L chain of (17); (19) an antibody having one ormore amino acid substitutions, deletions, additions, and/or insertionsin the antibody of any of (1) to (18), which has equivalent activity asthe antibody of any of (1) to (18); (20) an antibody that binds to thesame epitope as the GPR49 protein epitope bound by the antibody of anyof (1) to (18).
 10. The antibody of claim 1, comprising a human constantregion.
 11. The antibody of claim 10, wherein the antibody is a chimericantibody, a humanized antibody, or a human antibody.
 12. Apharmaceutical composition comprising the antibody of claim 1 as anactive ingredient.
 13. A cell proliferation-suppressing agent comprisingthe antibody of claim 1 as an active ingredient.
 14. An anticancer agentcomprising the antibody of claim 1 as an active ingredient.
 15. Theanticancer agent of claim 14, wherein the cancer is any cancer selectedfrom the group consisting of gastric cancer, colon cancer,hepatocellular carcinoma, lung cancer, ovarian cancer, Ewing's sarcoma,and glioma.
 16. A method for diagnosing cancer, comprising detecting aGPR49 protein or a gene encoding a GPR49 protein.
 17. The diagnosticmethod of claim 16, comprising detecting a GPR49 protein.
 18. Thediagnostic method of claim 17, wherein the GPR49 protein detection isperformed using an antibody that binds to a GPR49 protein.
 19. A methodfor diagnosing cancer, comprising the steps of: (a) providing a samplecollected from a subject; and (b) detecting a GPR49 protein contained inthe sample of (a) using an antibody that binds to the GPR49 protein. 20.A method for diagnosing cancer, comprising the steps of: (a)administering to a subject a radioisotope-labeled antibody comprising anactivity to bind to a GPR49 protein; and (b) detecting accumulation ofthe radioisotope.
 21. The diagnostic method of claim 16, wherein thecancer is any cancer selected from the group consisting of gastriccancer, colon cancer, hepatocellular carcinoma, lung cancer, ovariancancer, Ewing's sarcoma, and glioma.